Electrical gremlins have got me - help?
 

Hey guys - I am not very good working on electrical stuff so I know what is wrong with my truck will likely be something one of you has encountered, so here goes: my 64 2500 series truck operated flawlessly when I first got it a few months back, and all of a sudden for no apparent reason, my pass side stop light and pass side turn signal have ceased to work - no big deal right? So I change the bulbs in both figuring one of them is causing the other to not work, but same thing. I check to see if the lights work when the headlights are on, and the Right taillight comes on but that front rt park light does not still. Only the brake light does not work at the tailights; but nothing is wrong with the wiring that I can see going to the rt park light, and it worked when I got it, so what changed? Could it be the headlight switch or dimmer? Turn Signal switch? Not sure what to test or replace to fix this - I am thinking the turn signal switch is to blame, but cannot imagine what that has to do with the Right rear brake light not working unless that is affected by the outage up front....ideas?

Re: Electrical gremlins have got me - help?
 

I believe all of that is operated through the turn signal switch. You might get lucky and find that the big connector from the column is loose or dirty.
If that isn't the problem you can try using a hot wire to the corresponding terminals at that connector to determine if the problem is at the turn signal switch or a wiring problem in between.

Re: Electrical gremlins have got me - help?
 

Here's the link to Jolly's section on this issue.

http://6066gmcguy.com/Electrical-01.html

Re: Electrical gremlins have got me - help?
 

I have seen this quite a few times. sometimes its the left,sometimes the right. 95% of the time its in the turn signal switch. If you wiggle the switch arm you can sometimes get the stop light to work. Usually a good cleaning of the turn signal switch is all that is needed.

Re: Electrical gremlins have got me - help?
 

GMCNut: I agree with rest of the comments posted so far: check the turn signal switch. While the GMC switches seem to be a better design than the Chevy version, they are prone to getting dirty and if they ever get hot they cause small grooves to be melted in the plastic right near or at the contacts inside the switch. A good cleaning and possibly some light sanding or dremel tool work can smooth out these melted grooves, thus allowing the contacts to do what they are supposed to do. You'll have to remove the steering wheel. You will also have to be careful not to lose any of the upper column bearings when you remove the signal switch from the column. This is also a good time to clean the horn contacts. Test it before you reinstall the wheel. Good luck.

Re: Electrical gremlins have got me - help?
 

Remember...If that doesn't take care of it...
Grounds, grounds and more grounds.

Re: Electrical gremlins have got me - help?
 

Thanks guys - was thinking it was the turn sig switch and thankfully I have a reproduction switch on hand so I will try that and see if it fixes it....thank you!

Re: Electrical gremlins have got me - help?
 

I had bad luck with all of the repro turn signal switches. They do not allow the turn signal switch cup to attach to the steering column housing without interference. Then when you go to tighten the steering wheel down it causes the new turn signal switch to crack. Be careful and please let us know how the new switch fits/performs.

Re: Electrical gremlins have got me - help?
 

Greetings GMC Nut!

I also have to agree that you may have a faulty ground issue. If switch cleaning and/or replacement doesn't fix this, by all means look for a bad ground issue.

Re: Electrical gremlins have got me - help?
 

The after market switches are designed for the Chevy column. You need to remove a lot of the metal cup so the wires will go through in the right spot and cut off some of the turn signal arm. Or you can use a Chevy cup and arm. The chev stuff is really easy to find. I have done this at least 20 times, and while I prefer the better built gmc switch and bearing retainer reality trumps desire. Barry