Hitman's Pontiac Trans Am Forum
Trans Am Information => Trans Am Tech => Electrical => Topic started by: mikeb78ta on February 12, 2009, 09:42:04 PM
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Hey Guys,
Here we go again... I have read almost every thread regarding this much discussed topic. My questions are as follows
Temp/Oil Gauge
1. Neither of these work. I have checked as stated on many threads to move the wires from the senders and ground them. They do nothing when I do that they don't move at all.
2. There is voltage to the oil press. sender wire with the key on. Nothing happens on the gauge however. Not sure what else to do.
3. There is no voltage to the Temp wire??
Tach
1. I read that the tach connects to the distributor but should there be voltage to the 2 wires that goes to the tach at the dash with the key turned over??(pink/White)
2. which wire is for the tach at the distributor?
I went ahead and bought a new Printed Circuit from Ames. It should be here in a few days,but if its not that what else should I look for?
Thanks,
Mike
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DId your order the right circuit? There are two versions for 78.
On the Temp/oil pressure: pull the cluster and with the key on measure for voltage at pin number five of the white cluster connector (a pink wire). That should have voltage. My guess is you have a break in the plastic film circuit near the top of that line where it bends. It gets really thin at that point and that's where they tend to break. You're on the right track with a new plastic film circuit.
The tach is fed from a pink wire that comes out of the fuse box. That line usually has a fuse connector in it. Check the fuse.
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I hope I ordered the right one. I called in the order and spoke with someone. What is the difference? As far as the Tach goes where is the Fuse located? I had the steeing column unbolted and the cluster out today. I didn't see an inline fuse. Where is it located?
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Any other Suggestions? I went down to my car this morning and there isn't a fuse, but even more strange is that I only have 10.5 volts coming out of the pink wire feed. Could that be part of the reason my tach isn't working??
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On the circuit, it depends when your car was assembled. Earlier ones got a round tach cover on the back and later ones got a rectangular one. Thus, the physical dimension of the circuit assemblies are different and not interchangeable. The electronics are the same though. What exactly did you talk about with that guy? If he asked you the VIN or build date, chances are you'll get the right one. If he asked you whether or not you had rally gauges....it's 50/50. You'll know as soon as you see the circuit and look at your old one.
On the tach if you disconnected that pink line and measured the voltage....10.5 should be enough. The fuse is located on the pink wire. The fuse holder has the pink wire on either side. The fuse holder should be white. But if you're getting voltage with that wire disconnected the fuse should be OK.
Then you need to see if you're getting a signal from the distributor. There is a tab marked "tach" on the lip on the distributor where the feed wires come in. You'll need to consult with the service manual for the specifics...but you connect a light bulb to that wire with a probe....then at the RPM's go up...the light bulb gets dimmer. That means you're getting the right signal to the tach. A strange test...but that's what the service manual says to do. I guess you'd need a scope to really see the signal.
Does your tach just sit idle? Are both the brown and pink wires connected? The brown wire comes from the tach...although I think that wire changes color after exiting the firewall towards the distributor.
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Regarding the Printed Circuit, I will call Ames Today to make sure they send the right one. I did tell him that the The car has rally gauges, however he didn't ask anything else. I will confirm that I get the round back circuit.
Regarding the pink wires I found some pictures on the forum regarding the pigtail that comes off the fuse box. at both pink pigtails there is voltage. The brown wire to the distibutor is connected. I will try the light bulb test with the car running to check if anything happens. Also the 2 wires (pink/white) at the Tach itself are both there. I also purchased another Tach it also doesn't work so I ruled out that there was a possibility that the Tach is Bad.
Should I try to run a ground via a jumper to the back of the Tach and a good ground spot to see if there is a ground issue?
I guess I'm just running out of ideas. Thanks for the help
Is it possible that the brown wire that connects to the distributor may not be connected under the distributor cap?
By the way there definitely is no "inline Fuse" anywhere on the pink line or the brown to the distributor under the hood. I traced it from the tach harness at the dash to the fuse box???
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Well, I guess some of the pink tach wires had a fuse and some didn't. But after all these years you might not have the original wire anyway.
On the plastic circuit, tell ames you need the early 78 circuit (if you have the round tach plastic housing).
On the tach, yeah, it's possible you've got a back coil lead. Try the light bulb thing to see if your getting a signal. I'm not sure what a volt meter would tell you. The service manual doesn't suggest using one.....at least not that I could find.
If you haven't done a tune up, you could pull the cap and rotor and change them. And, also pop in a new coil and module. I do that every ten years or so to avoid getting stuck. The cap and rotor on my daughter's car gets replaced every two years....just before I get the car smogged. The coil and module ten years is about right unless you put lots of miles on the car.
The other thing to do is to trace that tach wire from the distributor to the tach just to make sure there aren't any breaks. Also, if you pull that connector off the tach.....don't break the ears....I hate that!!! When I see those connectors at the salvage yard I cut them off and bring them home.
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I had the car tuned up right after I bought the car 4 months ago. Would they have automatically changed the coil and module? The cap I know for sure is new. Delco. The rest I will try and get back to you. Is it possible there is no contact to the brown tach wire and its not getting signal? I'll try the light bulb trick, if nothing maybe there isn't contact???
I spoke with Ames and they said they only have a rally gauge and a non rally gauge circuit??? I will have to wait and see. I did tell them I need the Round Opening. We'll just have to wait and see. I'll keep you posted to let you know my progress. Something eventually has to come of this.. As always, thanks a lot for taking the time to walk me through this.
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I had the car tuned up right after I bought the car 4 months ago. Would they have automatically changed the coil and module? The cap I know for sure is new. Delco. The rest I will try and get back to you. Is it possible there is no contact to the brown tach wire and its not getting signal? I'll try the light bulb trick, if nothing maybe there isn't contact???
I spoke with Ames and they said they only have a rally gauge and a non rally gauge circuit??? I will have to wait and see. I did tell them I need the Round Opening. We'll just have to wait and see. I'll keep you posted to let you know my progress. Something eventually has to come of this.. As always, thanks a lot for taking the time to walk me through this.
When they installed the coil in the cap, they could have screwed up that tach wire...but check with the light bulb.
Ask Ames if the 77 circuit is the same part number as the 78 they are sending you. 77 should be the same part number as your 78. The later 78 circuits are the same as 79.
Ames doesn't know these cars like we do.
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I will check with Ames on the circuit.
One big thing I forgot to do when I hooked up the secondary Tach I have is to Gound It to the Chasis. I Did that to both Tachs I have. When I did it to the Tach that is on my car still nothing. When I did it to the secondary one it pegged it to 6000 and it stayed there.
I also took a lead and a Light bulb (12 volt car bulb) and hooked it up to the tach port on the distibutor Nothing happened. Am I getting any closer to the elusive Tach? I'm not sure...
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I will check with Ames on the circuit.
One big thing I forgot to do when I hooked up the secondary Tach I have is to Gound It to the Chasis. I Did that to both Tachs I have. When I did it to the Tach that is on my car still nothing. When I did it to the secondary one it pegged it to 6000 and it stayed there.
I also took a lead and a Light bulb (12 volt car bulb) and hooked it up to the tach port on the distibutor Nothing happened. Am I getting any closer to the elusive Tach? I'm not sure...
It's the signal from the coil. remove the top off the distributor cap and check the wires. Those wires are really thin and it could have broke. Also, they may not have it wired correctly. I don't remember off the top of my head the color wire combination and where they go. I always write it down before removing the old coil though. I bet they switched some wires.
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I have read up a little on the distributor. Is there anything in particular I should be careful of. I don't want to put anything out of order. Should I leave the - terminal on the battery or not? Sorry first time messing with the distributor. Thanks
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Oh Yeah 1 other thing does that mean that my original Tach is Bad? that one didn't do anything. Is the one that pegged potentially good?
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I'm not sure if your tach is bad or not. My guess is it's good. I always assume the gauges are good until I prove them bad.
You need to pull the cap. What I do....it's hoky....but I've been doing it the same way for lots and lots of years....I start with one plug wire...mark it number one with some masking tape. Then pull the wire around counter clockwise giving them the next number. I don't worry about the cylinder number...just how I pull them out. It's the way a moron does it. ;D
Then there are four spring clips that you can release with your fingers. Then disconnect the connectors and pull the cap off. Be careful with those connectors because the ears break very easily...so don't pry them open or you'll break them. I've never broke one but my daughters T/A had a broken one when she bought it but I had a spare.
There's a lid on top of the cap that's held with some fasteners. Remove the fasteners and you'll see the coil and the wires coming out from it and into that lip on the cap. Post a picture when you get there and we'll be able to see if it's connected properly.
You don't need to disconnect the battery...just make sure the ignition is off with they key out.
Good luck!
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Thanks so much for sticking with me through this. I feel like I'm getting closer. I will send pics tomorrow when I remove the cap. Much appreciated...
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Okay Here we go... I took off the distributor this morning as instructed. Here are the pics you asked for. Nothing to me seems out of the ordinary. All the wires look to have good contact?? What do you think?
(http://i548.photobucket.com/albums/ii354/mikeb78ta/MikesTa001.jpg)
(http://i548.photobucket.com/albums/ii354/mikeb78ta/MikesTa002.jpg)
(http://i548.photobucket.com/albums/ii354/mikeb78ta/MikesTa003.jpg)
(http://i548.photobucket.com/albums/ii354/mikeb78ta/MikesTa004.jpg)
(http://i548.photobucket.com/albums/ii354/mikeb78ta/MikesTa005.jpg)
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Replace the coil. It looks to me that you only have two wires going to the connectors. I think there's four...but maybe three. Also, your connector is broken. And, did you remove the connector closest to the cap or is it not there? I seem to recall a yellow wire that I don't see coming from your coil.
You should have wrap the tape all the way around the wire....just make sure those numbers don't fall off.
And I was totally in the land of Fords when I told you about the clips that hold the cap on :-[
See those screws....they hold the cap on. There's a little arm that swings under the distributor body and holds the cap secure. There's four of them. Turn them 180 degrees to free the cap. You'll need to pull the cap to replace the coil.
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Thanks,
I figured out the 4 spring clips(trial and error) ;) I am going to head to the parts store now. Is the coil all I need? Where are the Yellow wires suppossed to connect to?
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Thee yellow wire fits into one of those slots. Look at the coil before you buy it to make sure my memory is correct....but I'm almost positive you're missing a wire. You're missing a connector too.
Edit:
I think you've got all your connectors...there just broken..at least it looks that way to me.
We need someone who has recently done this to give you the correct wire/color slots. The manual doesn't give that information...just says to be careful to put them in the right slots. There's probably three wires that go into the slots and one ground. Your middle slot is empty.
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I went to the store to buy a new coil. They showed me the coil and it only has three wires(red, white, ground) I bought it anyways because the one I had was not new. Which connector is missing?? I have looked online also for a coil with an additional yellow wire can't find it? Any other suggestions. I will replacee the coil to start and see if there is a change.
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I'm pretty sure that middle slot needs to be filled. But, I could be wrong about that. I haven't changed a coil in a few years. But, your problem could be the connector too. They're really in poor shape. Make sure you get a tight fit.
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You must be right about the middle slot... I put in a new coil and everyhting worked.. the car started and unfortunately the same as before. I did the same checks as yesterday. I put both tachs on then I grounded them both Nothing except for the back-up tach pegged at 6000 again. If you can come across any Distributor pics for the 403cid that shows what goes in that slot, that would be awesome. When I took off the cap there were 2 yellow wire attaced to the base of the part that swivles(not sure what its called) they however don't attche near the coil however.
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You must be right about the middle slot... I put in a new coil and everyhting worked.. the car started and unfortunately the same as before. I did the same checks as yesterday. I put both tachs on then I grounded them both Nothing except for the back-up tach pegged at 6000 again. If you can come across any Distributor pics for the 403cid that shows what goes in that slot, that would be awesome. When I took off the cap there were 2 yellow wire attaced to the base of the part that swivles(not sure what its called) they however don't attche near the coil however.
PM Ldragon. He's knows the 403 backwards and forwards. And, he's a good guy.
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Roger that! I've gone as fasr as I can. Thanks for the help! Maybe tomorrow will be an easier day!!!
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The only other thing I can think of is the module. If you short that tach line to the block you destroy the module. So, the module is connected somehow to all this. I've never seen a schematic for the module or a good explanation of everything it does. I know it controls the dwell but that's as far as my knowledge goes on it.
But someone will come on and tell us how many wires the coil has coming out of it. I wouldn't have written down the colors and slots if it were only the white and red wires. But, it's been so long since I went through this and I usually scribble down the wire positions and then toss the paper. I guess I should commit this kind of stuff to memory. But when I'm doing a job like that, I just want to get through it as quickly as possible.
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No Problem I sent a message to LDragon, maybe if he gets back to me he'll have a picture or an explanation. It never worked since I bought the car so I have no idea what type of distributor or how many wires it had? this is definitely a good learning experience ;D
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It's not a wire that's missing. You're missing a little ground strap. It's made of the same metal as the other connectors comming off the coil. Here's a pic. It's the little odd shaped piece below the Accel coil.
(http://www.bakerperformanceparts.com/catalog/images/Accel_HEI_Super_Coil.jpg)
Without that the coil isn't grounded to the chassis since it is screwed to the plastic cap and nothing metal.
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See, I knew Larry would know. I forgot all about that ground strap. I knew there was something in that middle slot.
Thanks Larry, you're the best!!!
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Thanks Larry, now my next question is:
1. Can I buy just that piece?
2. Can you walk me through how to secure it from that center ground position to where it goes?
I can pull the cap and coil no problem if you tell me where it grounds to.
Thanks for the help.
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No problem. ;)
Installing it is easy. Just unscrew and lift up the coil. Slide the ground strap into the center slot and under the edge of the coil. Then just fasten it all back down. One of the screws goes through the hook at the other end of the strap.
I don't know about getting one by itself. Some replacement coils come with them. If someone has an old HEI (it can be out of any GM as long as it's the large car style like yours even, V6s.) it should have one.
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You didn't see anything in the box the new coil came in did you?
Oh, and on the wire colors. Some manufacturers use white instead of yellow.
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Yeah I did look in the box. It only had the new coil. Nothing else. Let me ask you something else. What about the ground wire that is in the picture? It does touch all metal with the coil? Is it becauser the coil then sits it the plastic housing? I will look for the ground strap in the meantime.
Based on all this from this post. I realize you can't see everyhting I see, but should this Tach do something? If I can ground this properly should there be a positive result? Thanks for your help
-Mike
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The wire that screws down to the the corner of the coil should have the other part attatched to it. I believe you get that when you buy a new cap. There will be a little bag with the rotor button with spring attatched, a rubber isolator ring, and the ground strap/ plug.
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It didn't . I'll have to go back tomorrow and see about getting the strap. If they haveit. There is something to be said of getting Original Parts. :-[
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Did you get a new cap?
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No, I just bought the coil. I had the car tuned up about 2 months ago. They replaced the cap and rotor. I don't think they replaced the coil so I did today. They may have replaced the coil, but it looked pretty rusty(see pics).
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It didnt looklike they replaced it, ( I usually clean the cover when I have it off also) looks like they didnt replace the module either. Go to your parts place tomorrow and ask for a cap, when they get it, open it and see if that strap/ground plug is there.
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I'm sure it was replaced because when I bought the car the cap was a different color. I'm not sure of the module. Great idea about looking at a new cap. Hell I'll by it all if I can get the damn Tach working again... ;) It's bizzare because even with the old cap it still didn't work... Unless the ground strap was missing from it as well???
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Well from the look of where the ground is, i would say they put it back where they found it. lol
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Good point.. That's how I found it so that's how it went back. ;) First do no harm right?? It's hard to find good help nowadays. Thank God for you guys on the forum. :)
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I just had a thought. Some of the early HEIs used a wire like this one rather than a metal strap.
(http://www.chevelles.com/techref/hei_files/image030.jpg)
If you are not able to find a strap then you might be able to make one similar to this using a piece of wire, an eyelet connector on one end and a male spade connector on the other. Then just push the spade through the center slot and into the connector coming up from underneath.
I would also recommend that you use the same screw for both the strap and the ground wire coming out of the coil just for continuity.
I think LOMILETA is right about caps coming with those straps too. I'm pretty sure Delco caps as well as coils are supposed to have those.
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Yes Larry, that is exactly what i ws talking about. Now you know what you're looking for Mike.
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You Guys Rock ;D ;) :)> I can definitely make that if I can't find the right one. I'll post tomorrow after I do it. Anything else you can thik of before I go to the parts store???
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This is getting Funny... I went out tonight, started the car, turned on the lights, ..........Everything was dim on the inside. courtesy lights, dome light, gas gauge not working, volt meter not working, dash lights(dim), turn signals showing they are on but no flash. I assume it's a ground issue, but who knows at this point. Any ideas???
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Is it possible when I removed the cluster so many times this week that the printed circuit(as bad as it is) ruined the ground?? I believe that all these problems come from te same circuit??? Am I wrong?
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That's very possible. The point where the main plug slides in and out of the circuit is a prime location for it to "delaminate". The circuit is made from several layers and the action of the plug rubbing against it can cause them to separate. If you look at this pic you can see what happens. The arrows show a couple bad spots. The bottom left plug connection is pretty obvious. I'm pretty sure the main ground connection is the lonely little one at the top right looking at it from this angle.
(http://i20.photobucket.com/albums/b230/SirLDragon/tech/cluster_03.jpg)
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Is it possible when I removed the cluster so many times this week that the printed circuit(as bad as it is) ruined the ground?? I believe that all these problems come from te same circuit??? Am I wrong?
The dome light is switched ground. Is the dome light dim when you open the door? or when you turn the headlight knob? or both? The dome light can get ground from three sources, the headlight switch and by opening each door.
Larry could be correct on the cluster circuit. Try running a ground strap from the metal cluster housing to some place on the body of the car....or a long wire to the block and see if that helps. If it does, Larry's correct. If it doesn't, you've got something else going on.
As for those coil ground straps.....I don't recall ever getting a new one with a coil. I vaguely remember reusing that part on the new coil. Before you got your tuneup, did the tach work? The guy who did the tuneup may have forgotten to put that back on.
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Didn't you already try grounding the tach? I think we might be going in circles. But maybe that's the problem with the lights and the other gauges.
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The Tach never worked. I will try to find or make a new ground for the center today. I'll let you know how it goes. As far as the dome light it was dim as well with the doors open. I replaced both of the door jamb switches recently, but they worked perfectly since then. I doubt that's it. I may not have put the cluster wires back in tight enough. I'm going down to the car now. I'll keep you posted in a little bit. It was too dark and I was too tired to look last night. Any other ground spots to look at?
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Didn't you already try grounding the tach? I think we might be going in circles. But maybe that's the problem with the lights and the other gauges.
I wasn't referring to the tach problem but the ground situation with the lights and why they are dim. He has multiple problems.
Was the engine running when the lights were dim?
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Didn't you already try grounding the tach? I think we might be going in circles. But maybe that's the problem with the lights and the other gauges.
I wasn't referring to the tach problem but the ground situation with the lights.
No, I know you weren't. But I thought he already tried grounding it before he asked about a ground problem again.
Maybe it is a combination of problems we're dealing with here.
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Could be, he mentioned grounding the cluster housing when he tried to get the tach working....then complained about dim lights after pulling the cluster several times. It's tough trying to figure out the exact situation sitting in front of a computer. It's amazing that we are able to solve so many problems without ever knowing exactly what's going on, just with some hints. And, with all the creative mechanics that short cut everything and hack things......I think we do a pretty good job of resolving things.
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Yes the lights were dim when I started the car. The headlights were on also. These items I was referring to before, were all fine before yesterday. That's why I thought that I might have done something in the process of trying to fix the Tach. The main problem was the dash lights, courtesy, dome and gauges malfunction. There were no problems with the any of the exterior lights.
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Let's go over exactly what your problems are. I know your oil pressure temp gauges aren't working. I've already told you how to trouble shoot that.
The courtesy lights......was it you that didn't have the door switches connected....and once you connected them they started working?
I don't recall a problem with the dash lights....was that another thread?
On the dim lights, how new is your battery? Were the headlights dim also? Usually, when my headlights are dim with the car running....I need a new battery.
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No that wasn't me. My courtesy lights always worked. It also wasn't me with the dash lights, the battery is also new.
Let's go over exactly what your problems are. I know your oil pressure temp gauges aren't working. I've already told you how to trouble shoot that.
The courtesy lights......was it you that didn't have the door switches connected....and once you connected them they started working?
I don't recall a problem with the dash lights....was that another thread?
On the dim lights, how new is your battery? Were the headlights dim also? Usually, when my headlights are dim with the car running....I need a new battery.
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Oh yeah, The headlights were fine and so were the tail lights and side markers.
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On the dim interior lights, do you have the headlight knob turned to the brightest setting?
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Yes the knob is at the highest setting. I just went to the store and the interior lights and gauges function properly only when the headlights are not turned on. When I pull the headlight knob out everything gets weird. I'm looking into it right now.
I think I may have some good news with the Tach, however. I finally convinced the guys at the parts store I was missing something. Some idiot did remove the ground strap to the coil. It will be here in 1 hour. I will keep you posted on that.
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Okay... I replaced the ground strap for the coil. I tested the Tach in my car... Nothing happened. I tried the spare Tach and it did the same as before. It pegged out at 6000 and didn't more after that. Is it possible that something could have happened to the coil because it wasn't grounded? I still have power going through the pink wire. How exactly do you try the light bulb trick? If I take a terminal lead and plug it into the "Tach" port on the Distributor I am supossed to hook it to a 12 volt bulb right??
As far as the other issue with the dim display and the faulty gauges. I am convinced that it is because of the bad shape of the printed circuit because when I move it around at the cluster of wires at the back it goes back to normal. I will have the new printed circuit sometime this week. Thank God...
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I just removed the cluster from my dash. Below are pictures of my 2 Tachs. The one on the left(round Green) is the one that came out of my cluster the other is the on that came off of E-bay(spare). The spare wouldn't fit the printed circuit so it fair to assume that one is from another year?? Maybe that has something to do with it?? I was going to put the spare in place to try that obviously that isn't going to happen. Could I possibly have (original tach) a bad Tach?
I guess the next step is to wait on the printed circuit then after that maybe by a new Tach?? Any suggestions?
(http://i548.photobucket.com/albums/ii354/mikeb78ta/Dash005.jpg)
(http://i548.photobucket.com/albums/ii354/mikeb78ta/Dash003.jpg)
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Have you checked the wire from the distributor to the tach for integrity?
As far as the two Tachs, the one on the left is 78 first style and earlier, the one on the right is later 78 and thereafter. That's why I was saying you have to be sure on the circuit. There were two types to accommodate the two different tachs.
As far as your current circuit, the picture is so out of focus I can' really see if there are any problems or not. Try using an ohm meter on the circuits to see if there is a break.
The oil pressure/temp circuit ends at that post above the "2" in the middle of the picture. Use an ohm meter on that circuit to see if there is a break. You did say that your oil pressure and temp gauges weren't working, didn't you? When both gauges are out, it's usually that circuit.
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Good point on the Tach wire to the dash. I'll go and se if there is continuity. As far as the Circuit. I know it's bad and I have checked for continuity there as well. As far as the ohm meter, I need to go by one.
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I forgot to ask you before. Is it possible the later model Tach wouldn't work with this car? Just throwing out there.
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I just got back from checking the Tach wire. There is a good continuity signal from under the hood to the dash. Do you think this is starting to sound like a distributor problem and not a Tach Problem? Is it possible that I should replace the cap, rotor, coil ,module???
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Both tachs should work.
The manual says to connect a test light to the brown wire which connects to the TACH terminal of the distributor. With the engine idling, a test light should light with approximately the same intensity as a 12 volt signal. As the engine speed increases, the test light intensity should decrease.
Do you have a volt meter? You said you measured 10.5 volts at the pink tach wire. Did you measure it with a volt meter at the connector with the connector disconnected and the ignition on?
Also, the tach is grounded to the cluster housing. There's a nut over the ground point that actually is the tach ground point. With the ignition on, measure for voltage at that ground point with your volt meter. There should be no voltage at that spot. You might have to put a jumper over that nut to make it easier to connect the volt meter.
I would do the volt meter tests before I used a test light on that brown wire....if you screw up with the brown wire you'll ruin the module.
When you tried the second tach...did you install it in the cluster or was it out of it? Because it wouldn't work unless you ground it.
By the way, if you do use a test light disconnect the connector to the tach and test it there. Then you'll know the wiring is OK too.
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I do have a volt meter. I used it quite a bit during this process. I was attempting to put the secondary tach in the cluster, but it wouldn't fit the circuit. That tach was grounded from the Ground screw from the tach to the chasis while the engine was running.
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I do have a volt meter. I used it quite a bit during this process. I was attempting to put the secondary tach in the cluster, but it wouldn't fit the circuit. That tach was grounded from the Ground screw from the tach to the chasis while the engine was running.
Buy a test light and check that brown wire. If you're getting voltage at the pink wire and the test light dims as the RPM's increase, you've got a bad gauge. And, you're sure that the tach ground that you installed today is making contact with the connector at the tach?
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Okay tomorrow I will buy a test light. I am absolutely sure I had a good ground. I put the jumper from the "GRD" screw to the door jamb switch. I checked today, with the car running, and I am getting 11.5-12.3 volts to my meter. So you want me to put the probe end to the wire coming to the dash and with the car running reve the engine. If the light goes dim, i am getting signal. Correct? I know it seems weird to have a bad gauge, butr I'm starting to think it has to be the gauge or a bad distributor, coil, module, rotor. What else could it be? Thnaks for all the help the past few days , if you were here in Ft. Lauderdale, I'd buy you guys a beer ;)
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If the test light goes dim when you rev the engine, then your gauge is bad.
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Okay so I went and bought the test light. I removed the Tach plug from the cluster, then I put the alligator clip from the lead to the power side(pink) wire, then touched the light to the Tach wire, fired upo the car and the light actually got a little brighter when I gave the engine some revs. Probably because the alternator increased in voltage. What next???
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Okay so I went and bought the test light. I removed the Tach plug from the cluster, then I put the alligator clip from the lead to the power side(pink) wire, then touched the light to the Tach wire, fired upo the car and the light actually got a little brighter when I gave the engine some revs. Probably because the alternator increased in voltage. What next???
You connected the test light to the wrong lead. Connect it to the BROWN wire that comes in from the tach (the other wire in that connector) Wow...I don't know what the ramifications of what you did will have on that circuit. One side of the light goes to the brown wire...the other side goes to ground. On a test light....one lead always goes to ground.
Also, check that ground nut on the back of the tach for voltage with the key on. Your circuit could be leaching voltage to ground which could cause problems with the tach.
OK, once you've done the test with the test light and you get it to dim with the engine RPM's increasing....and you've validated that there is no voltage at the ground nut....you've got a bad tach.
If you find voltage at the ground nut....probably a bad printed circuit.
If you have no signal at the brown wire (test light doesn't dim or doesn't light up), .....you've got a bad wire from the distributor to the tach.
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I'll go check it now, so should I connect the alligator clip to ground and the probe to the brown wire?
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I'll go check it now, so should I connect the alligator clip to ground and the probe to the brown wire?
You should have two wires from the test light. One goes to ground, the other to the brown wire.
Here's a picture. The alligator clip could be clipped to ground. Then either probe the brown wire at the connector with the probe, or connect a jumper between the probe and the brown wire...be sure not to ground that brown wire though.
[attachment deleted by admin, over 60 days old]
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I'll post a pic of what I have.
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Here's the test light I bought.
(http://i548.photobucket.com/albums/ii354/mikeb78ta/001.jpg)
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Okay we have the same light. I did what you said and I put the alligator clip on the ground then I put the probe end to the brown wire. The intensity of the light never changed.
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Alligator clip to ground....then probe brown wire with the probe. See my post above.
You're going to figure this out today!
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I also used a volt meter at the ground screw. It reads 0.17 volts.
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Geez, this is a tough one. Disconnect the tach lead at the distributor (It's marked "tach"). Connect the alligator clip to ground and probe the tach terminal (on the distributor). Just take care that you don't ground that terminal. You do have some who can rev the engine, don't you? Don't worry, it's only 12 volts at that point......but if your fillings start to heat up..... ;D
I think you've got two problems. Your circuit is leaking voltage to ground and your wire from the distributor to the tach is bad.
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Okay good Point. I'll go ahead and do it now. If the light goes dim at the distributor, I guess your right and the wire is bad. I'll be right back...
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So I attached the alligator clip to a ground, then I put the probe to the spot markedTAC on the distributor. My wife gave the car a good amount of revs and the light stayed lit, but did not change in intensity(up or down)
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Well, about all you can do now is pull the cap and check all the connections. Make sure all the terminals are straight. Visually check the connectors and make sure they will engage the terminals from the distributor correctly. When you put the ground strap on the coil, did you make sure you engaged the connector correctly?
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I'll double check all the connections. This is exactly how I put the ground strap in.
1. removed the cap, removed the coil.
2 put the ground strap in, then replaced the coil, put all the screws back into the hole and tightened snuggly.
3. The base of the ground strap and the top ground wire are on the same screw. put the cap back on,
4. plugged in the 3 wire cluster(ground) the red wire to the red wire plug from the alternator, Tach wire from dash to Tac on distributor
5. Put all the spark plug wires back to the proper terminals on the cap.
That's it!!
Is it possible that I just need to wait until I get the printed circuit. Also Is there way to test that the ground strap is actually doing it's job? I know the strap is plugged in properly and is making good contact with the coil??
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It's possible that the printed circuit could be your problem, especially if the ground at the coil is connected to the ground to the Dash wiring. If I get time, I'll pull the top off my coil and check the two wires. It's also possible they could be in the wrong slots. But don't change yours until we get confirmation. We don't want to switch things around without being sure.
To answer your question on the coil ground, you could follow the wire that attaches to that terminal and find out exactly where it goes...then find a good spot to measure voltage with your volt meter. There should be no voltage. If there is, you'll know thats the problem and your new circuit should fix that.
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Sounds good.. I'll go back down and check all the connections another time. I am sure the wires are in the right slots beacause the plug for the Tach and the plug from the alternator are different sizes. It's a stretch, but do you think I could have fried another coil? Are there any other items related to the distributor that could be bad? I doubt it's the wire going to the tach because there is good continuity and no visible breaks in the line.
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I don't think the tach is bad. But this is puzzling. Try finding the end to that ground wire to measure for voltage.
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I'll go and check the ground for voltage right now. By the time this is over I will have a whole new appreciation for what a tach really does ;)
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Okay so I went down and tested every ground from the distributor. There is no voltage. I also checked every wire for loose connections. Nothing is loose.
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I think your grounds are connected from the coil incorrectly. The ground wire coming out of the coil is grounded on the left side. The new ground you installed yesterday goes on the RIGHT side. See my crappy picture. Also notice that my ground is a wire with a terminal like the picture Larry posted. I think your's is all one piece of metal.
[attachment deleted by admin, over 60 days old]
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So what your saying is the new ground strap( funny looking bent piece of metal) that has a hook on it is suppossed to ground on the opposite side of the coil?? I'll give it a shot. It can't hurt. Right now I have them both on the same post. Let me go try it and I'll let you know how it goes...
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Well I was really hopeful with that, however it didn't work. I tried both Tachs also and the same as the past few days. My Tach does absolutely nothing, the spare just pegs out at 6000.
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I was hopeful too. If that test light stays bright all the time, it means you're not alternating ground/ungrounded.
At this point, since you measured voltage at the ground point of the tach you should wait until you get the new circuit in and then try. If the car is running, your coil should be OK.
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The new printed circuit will be here by Wednesday. Unfortunately I have to out of town for work tomorrow. I am also dropping my car off at Trans Am Specialties of Florida tomorrow so they can re pin my door hinges and adjust my leaking drivers side door so I won't be able to do anything else after today until 10 days from now. Oh well I wanted a project. I sure got One... ;D
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You've been all over this board! But that's how you learn. Once you get to the bottom of the tach problem you'll never have another tach you can't diagnosis.
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Thanks again for all of your insight. I will post again when I get back from my trip and get that circuit installed... Allit it is , is time and Money!!! ;)
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Hey Guys,
I just got back in town from a work trip. I received my new printed circuit and I installed it. I was glad to see that the oil pressure gauge and Temp gauge are now working. I am not so happy that it still did not resolve my Tach Problem :(. Any thoughts that the tach could be bad??
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At this point you should replace the tach. Buy a used cluster on ebay, or Classic sells new ones for gulp! $289.95. I'd go for the used cluster myself.
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I figured as much. there are a few I have looked at on e-bay. I will get my hands on the non-quartz style and let you know how it goes. Thanks.
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Okay. I am still really confused. I recently bought a used Tach off ebay. It is the same nono-quartz style as my original. I changed it out withe the tach that was in the cluster. the only difference is that is an 8k tach. It doesn't work. I changed out the printed circuit a few weeks ago as stated in previous posts everything else works. Any new ideas? I tested the coil wire with a test light and there is signal coming from the distributor. Thanks
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My only other thought is changing out the distibutor, everything else is new? What do you think??
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I wouldn't go into a parts changing mode. Do you know any old timers that might have a hand held tach? We used those to set the dwell in the old days. Connect the hand held tach and see if it responds. Also, that signal wire isn't simply a wire, it has a little part in it. I'm not sure what that does but it may be a diode kind of thing. Rick might know....he knows everything.
Basically all those tachs work off the same principle. 12 volts, ground and the signal from the distributor. They're set for four cylinder, six cylinder, or eight cylinder. As long as you have a tach from an eight cylinder, you should get the proper reading. That 8K tach may not be working. Or, if you have another car, you can connect the tach to that car if you know what you're doing.
Your printed circuit shouldn't affect the tach, unless there's a break in the circuit which leaks voltage to the cluster canister.
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Good idea about the hand held tach. Yeah I can get one from a guy I work with. I'll try that first. I am positive that i checked all the connections and that there is a solid ground at the new circuit and that all the steps you told me about before are connected properly, It just seems weird that all 3 tachs I have are bad? Im going out of town again tomorrow. I'll keep you posted when I get back. Thanks a lot for the ideas...
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I tried an 8000 rpm tach that I bought off ebay and it didnt work either.
The reason I bought the gage assembly was for the 160 mph speedometer. I think you must have got another bad one from ebay.
Also make sure your panel assembly is grounded or the tach wont work at all.
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I hear ya. I've thought about just buying a brand new one. I realize that it is nearly $300, but at least I can be sure of it working. I now have 3 that aren't working for me. Maybe they are good, but I know they aren't working for me. I've checked the ground and my new circuit was put back together by me and I'm sure it isn't a ground on the circuit at least, but thanks for the info regarding the e-bay Tach. Makes you wonder if someone is selling duds??? :(
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Connect the hand held tach at the tach connector first (the brown wire). Unplug it from the rear of the tach. You might have to run a jumper wire in order for the hand held tach connectors to reach the battery. Don't let that wire ground or you'll ruin the module. Check the rpm's at that place first. If it works, you know you're getting a correct signal from the tach. If it doesn't, connect the hand held tach to the tach terminal of the distributor to see if you get a signal. If you do, you've got a bad signal wire. If you don't, you've got a problem in the distributor. You did change the module, didn't you? I don't think the module's really involved but liked I said before, I've never seen a schematic of the module or a narrative of exactly how it works.
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No, I never replaced the module, only the coil. I ill give it a shot when I get back in town. I'll keep you posted as it goes. Come Hell or High Water I will fix this if it kills me. Thanks for the instructions.
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So I just got back in town and took a shot at this tach again. I figured I would bypass the 12volt and the coil wire coming in to the tach and run a jumper from the battery to the 12 volt on the tach and another jumper from the "tach"on the distributor to the "coil" on the tach to see if there was a bad ground or a split in the wire coming in from the firewall and it keeps doing the same as always... Nothing!!! As prevoiusly stated I have a hard time believing that I have 3 bad tachs.
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Just to be complete, ground the cluster canister with a jumper too. You do have the little nut at that ground place on the back of the cluster don't you? Where is says ground...that's for the tach. That's the only thing left. Did you ever try a hand held tach?
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Just to be complete, ground the cluster canister with a jumper too. You do have the little nut at that ground place on the back of the cluster don't you? Where is says ground...that's for the tach. That's the only thing left. Did you ever try a hand held tach?
Yes it was grounded as well. The only hand held tach a buddy of mine has is a "photo tach"?? Won't work for this application.
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I don't know what that is.
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I don't know what that is.
Yeah Me neither. He said it hooks up via the + and - termianals on the battery and I works by a signal as you point and hold it at the timing belt and it measure revolutions. Not obviously what I need. I figured when I by passed all of the existing wiring, I would get a result. I also used the test light as you told me about before with the new setup and I'm still not getting a dim signal as the engine revs. I realize you said before not to get into a parts changing mode, but at what point do I need to look outside the box and look for something beyond the tachs and wiring to the tach. Could something be impeding ground, underground in the distributor???
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It's got to be wiring. Here's what the service manual says:
1. Insure that the in line or fuseblock fuse is not blown.
2. Disconnect the connecter from the back of the instrument panel. Turn ignition on and check for 12 volts at the ignition input connecter (pink) and no voltage at ground (black). Connect a test light to the brown wire which connects to the "TACH" terminal of the distributor. WIth the engine idling, a test light should light with approximately the same intensity as a 12 volt signal. As the engine speed increases, the test light intensity should decrease.
3. If proper signals are present at the connecter, replace the gauge. If not, the problem is in the wiring to the gauge.
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It's got to be wiring. Here's what the service manual says:
1. Insure that the in line or fuseblock fuse is not blown.
2. Disconnect the connecter from the back of the instrument panel. Turn ignition on and check for 12 volts at the ignition input connecter (pink) and no voltage at ground (black). Connect a test light to the brown wire which connects to the "TACH" terminal of the distributor. WIth the engine idling, a test light should light with approximately the same intensity as a 12 volt signal. As the engine speed increases, the test light intensity should decrease.
3. If proper signals are present at the connecter, replace the gauge. If not, the problem is in the wiring to the gauge.
ta78w72 Thanbks for taking the time to go over this with me. As far as:
#1 The fuse is not blown. There There is no in-line fuse
#2 There is 12 volts present at the pink wire. With the new printed circuit there is no voltage at the black wire. With the test light connected at the Tach terminal. The light is normal at idle. It gets slightly brighter not dimmer at an increase in revs.
#3 I've replaced the Tach on 2 occaisssions. Which means I have 3.
I realize what you are saying and have followed everything exactly as you have given it to me. I consider myself to be pretty handy and The results are not showing it however. I am going to find the right hand held tach and try that next. I have read the service manual as well and it's frustrating when between what you tell me, what i have read and tried it doiesn't work. It should though. That's the tough part. Thanks again for all your help. I will give it another shot tomorrow.
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I know...I'm frustrated too!
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#1 The fuse is not blown. There There is no in-line fuse
That's a clue. There should be one, so the only way that there's not is that somebody's diddled with it. I'd take a hard look at that wire to see where it actually goes and how it gets there.
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#1 The fuse is not blown. There There is no in-line fuse
That's a clue. There should be one, so the only way that there's not is that somebody's diddled with it. I'd take a hard look at that wire to see where it actually goes and how it gets there.
How am I getting a signal and voltage then?? I am all ears This issue has been going on too long. I heard that some had inline fuses and some not. Please correct me if I'm wrong. Thanks
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My 78 has an inline fuse on the pink 12v+ feed to the tach. If you don't, like Rick mentioned, someone's been hacking away under your dash and more than likely rednecked a few things. First thing I would check is that wire to see if its been spliced or something.
Up next.....run a ground from the battery directly to the gauge pod. Now using a fused wire run from the + terminal on the battery to the + battery terminal on the gauge pod for the Tach. Lastly run a wire from the Tach to the TACH terminal on the cap. All things being equal you should get a tach signal now. If not....
1. Have you replaced the coil?
2. Control Module?
3. Are all your underhood grounds in place?
4. Not sure if it was asked yet or not but......was this car original an idiot lights car??? (ie. didn't have rally gauges and someone added them in?)
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My 78 has an inline fuse on the pink 12v+ feed to the tach. If you don't, like Rick mentioned, someone's been hacking away under your dash and more than likely rednecked a few things. First thing I would check is that wire to see if its been spliced or something.
Up next.....run a ground from the battery directly to the gauge pod. Now using a fused wire run from the + terminal on the battery to the + battery terminal on the gauge pod for the Tach. Lastly run a wire from the Tach to the TACH terminal on the cap. All things being equal you should get a tach signal now. If not....
1. Have you replaced the coil?
2. Control Module?
3. Are all your underhood grounds in place?
4. Not sure if it was asked yet or not but......was this car original an idiot lights car??? (ie. didn't have rally gauges and someone added them in?)
Well according to this, not all '78's had an inline fuse. I have traced both the 12 volt signal and the tach wire. They are from the original harness. Not spliced or hacked, thanks for the ideas though.
http://www.firebirdtransamparts.com/techinfo/harness/optionwire/optionwire.htm#rpm
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It doesn't matter if he has an in line fuse or not. He measured the voltage at the connector and has 12 volts at that point.
You are probably getting a weak signal. As brian mentioned...try replacing the control module. But as I said before, I don't really know how the module works because I've never seen a schematic for it.
You've checked everything....this is a stumper!
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It doesn't matter if he has an in line fuse or not. He measured the voltage at the connector and has 12 volts at that point.
You are probably getting a weak signal. As brian mentioned...try replacing the control module. But as I said before, I don't really know how the module works because I've never seen a schematic for it.
You've checked everything....this is a stumper!
I'm thinking of running a new coil wire then replacing the module. I know it's not a fuse issue like you said because there is clearly 12 volts. Should I replace the coil again when I replace the module? The car runs so does that mean the coil is good?
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I think your coil is OK. Try replacing the module...keep the old one for a spare/troubling shooting part. If that doesn't work, yeah, I'd try the coil again. But you just replaced that, didn't you? Did you keep the old one?
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Yeah I did replace the coil when I purhased the missing ground strap, But could it have gone bad due to a lack of the secondary ground? Unfortunately I didn't keep the old coil, but since they are pretty cheap, I may go ahead and replace it and then keep this as you suggested. If I do that along with the module. There isn't anything else we haven't tried...
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One other really stupid question....the coil you're using now....is it white wire or yellow wire?
The original one from the factory was white wire for a pontiac 400. Just throwing that out there....
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One other really stupid question....the coil you're using now....is it white wire or yellow wire?
The original one from the factory was white wire for a pontiac 400. Just throwing that out there....
I believe that it is white. I have the Olds 403 though. I'll go back and check though.
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Here's one other thought....
Try taking the tach physically out of the gauge pod and hooking it up as I mentioned above.
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Already Tried that as well. No Luck, but thanks anyways... ;)
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Well while I had the car apart today to replace the alternator field wire I figure I would go ahead and replace the module in the distributor and while I was at it run a new "COIL" wire from the distributor through the firewall and finish it at the tach hoping that would solve any doubts about the signal forn the coil at the distributor, NO LUCK. I have replaced everything now related to the Tach. Nothing has worked. I'm completely stumped. Oh yeah I tried the other 2 Tachs I have Also, Neither of them worked either. ??? ??? ??? ??? ???
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It has to be the signal from the coil...has to be. If your test light didn't dim the signal isn't reaching the tach. Look for an old guy at work...one that's at least as old as Rick and myself. Ask them if they have a dwell meter. They have the tach built into them. There has to be at least one person that has one.
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I will find out about the dwell meter. I am considering taking my car out of commission for a month or so anyways. Long overdue for a much need paintjob and engine rebuild. I will get to the bottom of this eventually. Thankfully I will be intown for the next couple of months without any travel for work. That will give me more time to go through things slowly and find more little Gremlins... Thanks again for all the advice. It has definitely paid off...
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Did you ever figure this out? I'm having the same problem with my 81(converted to 73)
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I don't think it was ever resolved on this site, as I have the same problem too. I have looked at most of the different threads on this subject, but still can't get mine working. I might have to just spring for the cash and get a new tach. I'm starting to think it is a 403 problem. Most of the ones I have seen are late 78 on that folks have trouble with. Don't think many tach's on the Pontiac motors had problems. Let me know if you get yours working, and I will post what I did to get mine working, if I ever do.
Thanks.
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There is no distinction between a "pontiac" tach and a "403" tach. Those clusters are interchangeable.
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Well it has almost a year since this thread has been replied to. I still have not got my Tach working correctly, just checking to see if the others did? I'm beginning to think mine might be in the distributor. Please let me know if you were able to solve the problems encountered, and how you were able to solve them. I will continue to do the same.
Thanks.