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Old 10-09-2014, 07:31 PM   #1
kentucky_smith
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No rear running lights

'72 C10 Custom.

Can't quite figure this one out. Wires from the engine side of the firewall to the lights themselves are good. Brakes and turn signals work fine, but no running lights on the back or sides. All front lights work. I replaced the turn signal switch a couple of months ago, but they worked after I did that. Can't quite figure out where the wires go from the firewall inside the cab. All fuses are good and if it was ground, nothing would work.

Everything is as it left the factory.

Idears?
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Old 10-09-2014, 07:58 PM   #2
LockDoc
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Re: No rear running lights

Quote:
Originally Posted by kentucky_smith View Post
'72 C10 Custom.

Can't quite figure this one out. Wires from the engine side of the firewall to the lights themselves are good. Brakes and turn signals work fine, but no running lights on the back or sides. All front lights work. I replaced the turn signal switch a couple of months ago, but they worked after I did that. Can't quite figure out where the wires go from the firewall inside the cab. All fuses are good and if it was ground, nothing would work.

Everything is as it left the factory.

Idears?

That is not necessarily true. Bad grounds will cause some really strange behavior including exactly what you are experiencing.... It could also be the headlight switch. I would first disconnect the connector at the rear crossmember and test the individual contacts there. If everything is OK there then I would install a ground wire from the bed to the frame and see what happens.

LockDoc
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Old 10-10-2014, 09:50 AM   #3
68gmsee
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Re: No rear running lights

^ Agree....

Grounding could be the main problems. I fought rear brake light problems and other assorted problems on my 68 GMC until I installed new grounding straps all over the truck -5 to be exact. Old, rusty bolts from cab and bed to frame were the main problem.

I installed a ground from rear of bed to frame under the bed.
Another one from the bottom rear of cab to the frame.
Replaced the factory one on the rear of engine block to frame.
New negative ground cable from battery to engine.
Installed one from radiator support to battery negative (voltage regulator is grounded to radiator support).
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Old 10-10-2014, 11:03 AM   #4
cdowns
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Re: No rear running lights

it left the factory without the lights working?? strange
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Old 10-19-2014, 10:16 PM   #5
kentucky_smith
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Re: No rear running lights

Finally had time to work on it. No juice at the back plug for that wire. Ended up being a loose splice on the frame rail. Thanks guys.
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Old 10-20-2014, 07:32 PM   #6
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Re: No rear running lights

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Originally Posted by kentucky_smith View Post
Finally had time to work on it. No juice at the back plug for that wire. Ended up being a loose splice on the frame rail. Thanks guys.

Glad you got it sorted out. That kind of stuff can be really fun...NOT!..

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