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Old 09-16-2009, 07:01 PM   #1
hgs_notes
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Front side marker light problem

I'm working on getting all the lights on my 72 Jimmy working properly, and I'm doing pretty good, except for the front side marker lights. The driver side one works, but is dim. The pass side did not work at all, then after moving some wires around, it did work, then quit again. I can't find any problems with the wires, splices, etc.

The wiring diagrams all show the side marker lights having a brown positive lead, then a black ground wire, but that's not what I have. Mine is a brown wire and a blue wire. The blue wire ties in with the front parking/signal light. Interestingly enough, that is how the 73 and up trucks are wired. This is the same as the light wiring on my 71 C-10 also.

The only other problem so far is the turn signal circuit isn't working. The flashers worked, blinkers not so much. I've tried 3 different flashers. Two of those worked for sure on my C-10. Any thoughts or ideas appreciated.
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Old 09-16-2009, 07:03 PM   #2
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Re: Front side marker light problem

Try spilcing in an additional ground at your side marker lights. See if that helps.
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Old 09-16-2009, 07:39 PM   #3
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Re: Front side marker light problem

Dim lights are from a bad ground. I bet this is your problem.
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Old 09-16-2009, 08:26 PM   #4
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Re: Front side marker light problem

I doubt it is a ground problem. Front side markers that are wired like this one are not grounded the traditional way. One wire goes to the parking light circuit, the other wire to the turn signal circuit... both are positive.
I would follow the brown wire (parking light side) till you find some damage or corrosion. Added resistance will kill the light output too.
As for your turn signals, do you have both front and rear lights hooked up and working?
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Old 09-16-2009, 08:57 PM   #5
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Re: Front side marker light problem

Longhorns right, you cant ground the front side markers. Well you can, but your just cutting the turn signal wire and using it as a ground. I swapped the hazard and blinker flashers around and got them to work.

Odd things keep coming though. With the headlights on, the tail lights all look good, driver side front marker is ok, passenger side front marker off, left turn signal will not work, right turn signal does.

Headlights off, all the blinkers and front side markers work, but the left side is slower than the right. I think I have bad connection in the left blinker tail light wire. I think there is a problem with the right front blinker wires too.

I'm getting there though. I think on the front blinkers, the blue wire is the positive and the brown acts as a ground for the side marker lights, then switches for when the parking lights are on. I THINK anyway.
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Old 09-16-2009, 09:48 PM   #6
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Re: Front side marker light problem

Here's a diagram.

The brown wire is positve with the lights on it flows through the side marker and taps into front park/turn light it flows to ground through the turn light filament of the front park/turn light. With the turn signal on that side of the front park/turn light now has power and does not allow the marker light to flow to ground thats why it flashes on the taillight circuit (just like when the alt dummy light has positive power on both sides it goes out). Check the grounds on both front park/turn lights including the bulbs and sockets.
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Old 09-16-2009, 10:14 PM   #7
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Re: Front side marker light problem

Quote:
Originally Posted by fixit-p View Post
Here's a diagram.

The brown wire is positve with the lights on it flows through the side marker and taps into front park/turn light it flows to ground through the turn light filament of the front park/turn light. With the turn signal on that side of the front park/turn light now has power and does not allow the marker light to flow to ground thats why it flashes on the taillight circuit (just like when the alt dummy light has positive power on both sides it goes out). Check the grounds on both front park/turn lights including the bulbs and sockets.
Excellent! That diagram is much easier to follow and your explanation is spot on. I didn't have the parking lights mounted, which is why there was no ground for the side markers. I should be able to get all these babies working soon.
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Old 04-25-2011, 12:24 AM   #8
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Re: Front side marker light problem

Thanks for the diagram
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Old 05-29-2019, 04:37 PM   #9
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Re: Front side marker light problem

This diagram is the best! Helped me with a few wires and re-wiring for LED's. Thanks so much!!
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