Topic: **FIXED** Low Voltage, jumping needle, need serious help

[ta78w72]

Make sure the belt is tight.  I think you've checked all the wire connections like the positive and negative battery wires.  Those aren't corroded, are they?

[shadowrider]

I had a alt that tested good at autozone once  but it was not good, there machine said mine was good when tested, but when I drove the car  & used the lights wiper, heater it did not charge enough.  I had them replace it any way, & my problem was solved, for some reason there test machine showed it as OK, but it sure was not ok when I was using my lights & heater or wipers, this was my experience on one alt.

[ta78w72]

Like in my 99 Trans Am, I get voltage drop as the car warms up.  When it's tested cold it's OK.  I just haven't got around to replace the alternator yet.

In billknobbe's case I believe he's already replaced the alternator.

[Wild Bill]

Yeah replaced the alt already...
I didn't have them bench test my alt either, had them do it while in the car...
this happens all the time, not just when it's cold.... my battery never drains dead so I know that the alt does in fact work at least enough to charge the battery
the belt is new and tight, I might even take the belt off again and scuff the pulleys just to make sure that it is gripping good

[ta78w72]

Yeah replaced the alt already...
I didn't have them bench test my alt either, had them do it while in the car...
this happens all the time, not just when it's cold.... my battery never drains dead so I know that the alt does in fact work at least enough to charge the battery
the belt is new and tight, I might even take the belt off again and scuff the pulleys just to make sure that it is gripping good

There's a procedure in the service manual to isolate the problem.

[Wild Bill]

the only one i found dealt with dummy lights not rally gauges

[ta78w72]

the only one i found dealt with dummy lights not rally gauges

Well, you're right.  I thought there was something more in that section.  That section will only deals with symptoms and varying  voltage isn't one they cover.  Run it for awhile and then measure the voltage of the battery to see if it's undercharging.  If it is, that's the symptom you want to check.  If it's not, I really don't know what to tell you.

Maybe someone else has some ideas.

[Wild Bill]

Done that already, it's not undercharging

[Rick]

Well, let's review what you say it's NOT...

The alternator has been tested in the car and it's NOT that.
The voltmeter in the dash agrees with the digital voltmeter you are using, so it's NOT that.

I'm going to assume that you've had the battery checked, right?  You need to do a load test on it, not just a voltage check, to eliminate the battery as a possible source of the problem.  If you have another battery around (like in your DD), you can just  swap it in to check if the problem is still there.  Or you can take your battery in and ask them to load check it.

Now, provided it's NOT the alternator, the voltmeter, or the battery -- then it HAS to be something in between.  What's in between is wiring.  You can isolate the wiring by selectively removing fuses from the fuse block.  Check the chassis wiring diagram to see which circuits (fuses) are need for the car to start and run, then start pulling non-essential fuses and recheck for the problem AFTER EACH removal.  That will tell you which circuit is causing your voltage to waver all over the place.

The ONLY other thing that I could think of would be if the redundant ground connection was missing or screwed up.  That goes between the bell housing (or auto transmission flange) and the subframe on the passenger's side.  It is as big as the battery cable -- one end bolts to the engine/transmission and the other end bolts to the subframe.  People don't know what it is, so when engine/transmission work is done many would-be mechanics toss it, figuring it's not necessary.  It provides the extra grounding needed in cases like this, but the problems don't pop up right away.  You might check and see if that cable is present and properly connected.

[brian c]

Bill, Where in NY are you located? I have another gauge pod we could test with. I'm in Akron (near Buffalo). PM me if you want a hand!

And I'd wager its a bad ground or bad connection. Either the terminals in the connector at the gauge pod or at the bulkhead connector. Did you try taking a couple wires and connecting the volt gauge directly to the battery? Did the readings stabilize?

[Wild Bill]

Actually No, I hadn't even thought about hooking the gauge right up to it because I have been using a digital multimeter to hook up to the battery and the alt output. I am pretty sure that it has to be a wire, which is why I bought a new wire harness, the thing about that is, I keep trying to move those wires and what not to see if I could get a stable read or at least a full drop and nothing.... My harness tried to deliver yesterday while I was at work, I wasn't home so I should get it today, I'll hook it up later tonight after I get it and I hope that it fixes it, if not, I will get in touch with you Brian cause I really am throwing money at this and it's making me extremely mad, back home the people at Auto Zone are are ASE certified Gods and up here in Northern New York I had a woman who didn't know what a power steering pump was... I live up in Clayton, 20 miles north of Fort Drum, about 3 hours away from Buffalo

[72StreetBird]

I'd try the battery. Have it load tested. The battery should adsorb the shock of the load changing. If the battery is demanding 15 volts from the alternator something is wrong with the battery.

[Wild Bill]

Thanks everyone for all your help...
Just to re point out, before I posted on here I had already had the battery, alternator, and belts, and wiring going into the alternator replaced.. then I had the system load checked and had the battery load tested, I had checked all the grounds and even re ran more grounds to help with the problem...
Last night I got my new engine wire harness, disconnected it from the bulkhead and the battery and the alternator and the oil sending and temp sending units and the distributor... then i went to take off the bolts on the starter solenoid..
First off, without dropping the header it took about an hour for each bolt to come completely off and then back on with the new wires...
Here is the kicker though and I feel like a fool for not taking the time to actually check this first because I thought, "Nah, can't be that"
The two bolts on the solenoid holding the wires, were loose, really loose, guess the vibration from the motor knocked those things plum loose over the last 2 years...
Just for kicks I went ahead and changed out the harness anyway since I did pay 140 bucks for it and it is brand new...
After all said and done, started it up, started turning on accessories and the needle barely moved and then stayed put, it didn't bounce around or jump... then put it in drive and done it all the same too and it still worked the very same
So we can put this one in the category of check ALL connectors not just the ones you can physically get to from the top
My take is that the grime on the terminals must have held those wires together then when I pulled the wire off the alternator the first time it moved it free a little

[72StreetBird]

Did you have the lock washers or star washers on both studs? I'd hate to have tham work loose again. 

[Wild Bill]

Yeah, it was a pain though, didn't want to drop the header to reach it and had to use finger tips working my way through the header pipe on the side