No rear running lights - The 1947 - Present Chevrolet & GMC Truck Message Board Network

kentucky_smith · 10-09-2014, 07:31 PM

'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?

**LockDoc** · 10-09-2014, 07:58 PM

Quote:

Originally Posted by kentucky_smith

'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

68gmsee · 10-10-2014, 09:50 AM

^ 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).

cdowns · 10-10-2014, 11:03 AM

it left the factory without the lights working?? strange

kentucky_smith · 10-19-2014, 10:16 PM

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.

**LockDoc** · 10-20-2014, 07:32 PM

Quote:

Originally Posted by kentucky_smith

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!..

LockDoc

10-09-2014, 07:31 PM	#1
kentucky_smith Registered User Join Date: Feb 2014 Location: Outer Bluegrass, Kentucky Posts: 71	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?

10-10-2014, 09:50 AM	#3
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	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). __________________ 68 GMC 250/3 speed Saginaw p/b p/s 69 Chevy 350/350 currently in pieces still lookin for a cab 06 Trailblazer I just want a vehicle that I can work on, that won't talk to me, leave error msgs or keep track of how I drive...

10-10-2014, 11:03 AM	#4
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: No rear running lights it left the factory without the lights working?? strange __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY

10-19-2014, 10:16 PM	#5
kentucky_smith Registered User Join Date: Feb 2014 Location: Outer Bluegrass, Kentucky Posts: 71	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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