66 tail light and brake light snafu

[jocko]

Good evening folks - quick head-scratcher question about my lights (this could probably be in the electrical forum, but it's on a 66 chev truck, so coin toss - more people here anyway - someone's bound to be smarter about electrical stuff than me. Ok, ANYone is smarter about electrical stuff than me.... )

Someone told me last night that my brake lights weren't working. I checked when i got home, and they only worked if I pushed the pedal almost all the way down, which is why the guy that told me that didn't see any lights, I was using light braking coming slowly to a stop at the time. So, I assumed I needed to back out the brake light switch a little so it would come on with less brake pedal travel. Did all that adjustment, got it all back together - and shazam, no running lights, nothing. The headlights are the only things that come on now. No turn sigs, no front parks, no tails or brake lights. Checked all the fuses - all are good to go. All bulbs good to go. pulled the tail light bulbs and checked for power at the taillight receptacle - and there is none. So, I imagine same at front also.

Any ideas? There's only 2 wires on the brake light switch - and just in case I crossed them, I swapped them - still no go.

I like metal things I can get my hands on - but trons scare me. Thanks for any help.
Jocko

[DPowers]

I would start checking your grounds.

[Rich 5150 69]

Run a ground wire even if just a test wire from the taillight housing to the cab and see if things improve, you may have the same issue with the front running lights.

[jonzcustomshop]

I had a problem with both ground, and the harness from the turnsignal at the column.. cleaned up the connections there and that helped.

[jocko]

Thanks - just seems that usually if something stops working AFTER I do something - then it's probably something I screwed up... But it's kinda hard to screw up a brake light switch. I looked at a 62 wiring diagram I had handy (some differences from a 66, but light circuit shouldn't be much different) - and noticed that one wire on the brake light switch goes into the main harness and out to the front park lamps, but the other goes into the turn signal switch/harness. That falls in line with one of the comments above - and I know I've been having bad problems with my turn signal switch lately, was planning on replacing - so maybe it gave up the ghost before I got around to replacing it. I hope so anyway. Will tear into that tomorrow.
Thanks again.

[markeb01]

Perhaps you can get a small mirror up under the dash to see if you may have inadvertently pulled a wire off the headlight switch when you were wiggling things around by the brake switch. Also check if there is a turn signal harness connector near the bottom of the column. I'm not familiar with a 66 harness, but that could also have been wiggled lose working on the brake circuit. Turn signal wiring can drive you nuts without a diagram. The "crossover" circuit is the wild card. This is what allows the blinkers to keep working when the brake pedal is depressed. If that has failed in the turn signal switch, replacement is the only remedy.

[lakeroadster]

Jocko,

If you are like me you want to start with the easy fix and go from there. As has been suggested by others you may have a grounding problem.

Make yourself a test ground wire and attach it to a good known ground, then touch it to the tailight housing. See if that fixes the problem.

If it does fix it then make a permanent ground wire connection.

My grandfather had a '72 C20. It had wierd stuff going on, such as when he would hit the brakes all the parking lights would come on very dim, and when the turn signals were activated all the other parking and brake lights would also come on very dim. The ground wire technique fixed all those problems.

Good luck and let us know what you find out!

[Rich 5150 69]

That was my problem as well, permanent ground wire from the housings to the cab fixed all.

[jocko]

Hmm, sounds simple enough - thanks, will give it a try. And I AM like you all - simple first. Will give that a try and then probably dig into the turn signal sw/wiring if that doesn't work - have been having "issues" with the cnx cam and the switch is real sloppy - so probably need to replace it anyway, even if it's not the problem. But I just want to get the lights fixed first so I can get driving it again! I'm going simple today - no crawling around under the dash today, threw my back out big time yesterday doing that. I forgot how wiring can be a workout. Thanks again gents, appreciate the great advice - will let you know what I find out.

[shark66]

I had the same problem with my 66 when i first bought it. However mine turned out to be the pigtail wires running to the tail lights would hit against the metal tail light housing and short out. Electrical tape solved the problem.

[jocko]

success(!) Kinda anyway - turns out I am my own worst enemy. It WAS the simple answer - one should not hang one's shop light on wiring harnesses...

I unplugged a firewall connector somehow - approx mid-firewall, which is why I couldn't seem to figure out what happened - it was nowhere near where I was working.

So, brake lights were working great until the pushbutton of the switch popped out and rolled under the bench, somewhere, never to be found again.

But at least I figured out the big problem. Now just need to replace the brake light switch.

One more question has come up though - the FRONT parking lights - do they only come on when the headlight switch is in the half-way up position, i.e. running lights only - and NOT come on when headlights are on?

Seems I remember this is the way my 65 Impala used to work, just wanted to verify.

Thanks again for all the help - much appreciated.
Jocko

[jonzcustomshop]

correct on the park lights.
markbe01 (or is it captianfab?)has a thread on how to get them to run with the headlights on...
I just saw the thread the other day...

[jocko]

thanks - I will look it up. Gotta get em workin the way the factory did first though! But that confirms what I thought. Thanks.

[markeb01]

Here are a few threads showing how to convert the parking lights to running lights:

http://www.6066gmcguy.org/parklamp6063.htm

http://www.stovebolt.com/techtips/el...inglights.html

http://67-72chevytrucks.com/vboard/s...ht=park+lights

[jocko]

markeb01, thanks very much, that's good gouge!