Author Topic: Front running lights quit working - 1/6/07 Fixed  (Read 9517 times)

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Offline rkellerjr

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Re: Front running lights quit working...
« Reply #30 on: January 05, 2008, 10:22:07 PM »
Hey Rick, 75fire, over at TAC, indicates that the marker and grill light blink at the same time.
Rich

Offline ta78w72

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Re: Front running lights quit working...
« Reply #31 on: January 05, 2008, 10:26:47 PM »
I'm going to re-do that ground coming from the harness first and see what happens.  Then I'll volt meter stuff, weeeeee

Don't redo the ground.  Check it with your volt meter first.  If you "redo the ground" you're not really isolating the problem...that's more like parts changing.  To check the ground, if you can stick a small wire into the connector for the parking lights at the black wire....then attach one of your ohm meter leads to it and the other to the frame....see if you've got a completed circuit.  If you do, and I suspect you will, then move on to the brown wire of the bulkhead connector and measure for 12 volts.  I do suspect the brown wire.  I'm anal when it comes to ground though...I always check and I always suspect ground. 

Good luck!

Offline ta78w72

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Re: Front running lights quit working...
« Reply #32 on: January 05, 2008, 10:28:59 PM »
Hey Rick, 75fire, over at TAC, indicates that the marker and grill light blink at the same time.
Hey Rick, 75fire, over at TAC, indicates that the marker and grill light blink at the same time.

They have to blink at the same time because they are on the same circuit.

Offline Rick

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Re: Front running lights quit working...
« Reply #33 on: January 05, 2008, 11:44:31 PM »
OK -- something's getting lost in all the words, like ta78w72 says...

Here's a pair of videos to illustrate what I'm trying to say...

Headlghts OFF...



Headlights ON...



The differences are (a) with the headlights OFF, the lights blink in synchronization, and (b) with the headlights ON, the front turn signal bulb is dimly lit and blinks brighter ALTERNATELY with the side marker light.

Do the vids show that?  I hope so -- lotta jacking around to show it... :-\ :-\

Offline ta78w72

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Re: Front running lights quit working...
« Reply #34 on: January 06, 2008, 12:16:05 AM »
Rick,
See, you learn something new all the time about these cars!  I never really noticed that before.  I checked my car and it does the same thing.  Which indicates that the brown circuit is out of whack on Rich's car.

I have no idea why it works that way though.  The blue wire from the blinker circuit is shared by both those lights.  I guess I'll have to look at my spare harness one of these days to really understand what's going on.

Offline rkellerjr

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Re: Front running lights quit working...
« Reply #35 on: January 06, 2008, 07:39:19 AM »
OK, now we are getting somewhere.  With my headlights on, they are blinking at the same time, whicih they should blink alternating.
Rich

Offline Rick

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Re: Front running lights quit working...
« Reply #36 on: January 06, 2008, 11:07:26 AM »
HOORAY!  Success in communicating!

Actually, I think *if* we can figure out WHY that's not happening on Rich's car the problem will be pretty simple to fix. ;)

Offline Joker (告r茺agon)

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Re: Front running lights quit working...
« Reply #37 on: January 06, 2008, 01:27:11 PM »
The reason the front bulb is dim then bright in the 2nd vid is because it has two filiments. The dimmer of the two is the parking light fed by the brown wire.

Ok, I hope this helps to explain how they work.

Here is a modified copy of the Autozone wiring diagram.



I simplified it to show only what we are talking about. I also colored the wires to make it a little clearer.

In some ways we are talking about 4 circuits here even though there are only 2 pairs of bulbs and only 3 pairs of filiments.

In the grill we have a single pair of bulbs, but they each have 2 filiments. A dim one for the parking lights and a brighter one for the turn signals.

  • The bright side gets power from the fuse box, through the flasher, through the t/s switch in the column and then through the blue wires to the bulb then directly to ground at a point near the bulb on the core support. Pretty straight forward circuit.
  • The dim parking light filiment gets it's power from the headllight switch, through the bulkhead connector, down the brown wire to the bulb and then to the same ground as the t/s side. Also (and even more so) very basic.

Then there's the side markers. Here's where it gets a little weird since, as you can see in the diagram they have no visible ground. This is where most people get turned around.

  • When the headlights are off and you use the turn signals they are pretty simple. Power comes through the blue wires to the bulbs just like for the front. The ground is actually in the headlight circuit.
  • When the headlights are on and the turn signals are off they are also pretty simple. Power from the headlight switch comes down the brown wire to the bulb. But now the current is flowing the other direction and the ground is in the turn signal circuit. (I've heard different oppinions as to exactly where but for this particular problem that's not really important.)
  • Now - when you have the headlights and the turn signals on at the same time this is what happens. Like before, the marker light power is coming through the brown wire making that hot rather than a ground. When the flasher sends power through the blue wire that side also becomes hot, interupting the ground on that side. This causes the bulb to go out until the flasher opens and the t/s side becomes the ground again. This makes the bulb flash opposite to the front turn signal.

« Last Edit: January 06, 2008, 01:29:23 PM by SirLDragon »
Larry


Offline rkellerjr

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Re: Front running lights quit working...
« Reply #38 on: January 06, 2008, 04:54:14 PM »
Thank you Larry, that was very helpful.  I found out what the problem was and it's fixed.  Everything working appropriately.  The brown wire receptor in the fuse box was not making a good contact.  I may have bent it slightly or something but, I played around with it and then put the block back on and everything worked just fine.

Thanks everyone for your help!
Rich

Offline Joker (告r茺agon)

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Re: Front running lights quit working - 1/6/07 Fixed
« Reply #39 on: January 06, 2008, 05:00:44 PM »
Nice! Glad to hear you didn't have to rewire the whole circuit.
Larry


Offline Joker (告r茺agon)

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Re: Front running lights quit working - 1/6/07 Fixed
« Reply #40 on: January 06, 2008, 08:38:49 PM »
Just in case they fail again. Here's something you can use. Just hold this up in your window so people know what it should look like. ;)



Larry


Offline rkellerjr

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Re: Front running lights quit working - 1/6/07 Fixed
« Reply #41 on: January 06, 2008, 09:44:41 PM »
hehehehe!
Rich

Offline w72transamowner

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Re: Front running lights quit working - 1/6/07 Fixed
« Reply #42 on: January 06, 2008, 10:05:12 PM »
Show off...  ;D  ;)

Just in case they fail again. Here's something you can use. Just hold this up in your window so people know what it should look like. ;)




1978 Trans Am WS6/W72, Auto (purchased Sep 00)

http://www.motortopia.com/garage/cars/carfanatic1


Offline Eagle 1

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Re: Front running lights quit working - 1/6/07 Fixed
« Reply #43 on: January 06, 2008, 10:56:14 PM »
Quote
Check the brown wire for 12 volt.  That's the circuit that's controlled by the switch.  The other circuits, the blinking, is done with the turn signal.  When you pull the headlight switch out to the first position, you should get those lights on.  Then the second position turns on the headlights so that both sets of lights are on.
Quote
The video did explain quite a bit.  It was worth putting up.  It made it obvious that it wasn't the bulbs.

Good work ta78w72. ;)
" He done good didnt he Fred?"
"I'm in pursuit of a black Trans Am. He's all mine so stay outta the way."