Intermitent Headlights

[Tynee]

Buddy of mine just bought a '71 Jimmy (That's right, we managed to make his wife mad at us both in one purchase. It was my fault he bought that "old redneck truck"). Anyway, when we went to check it out, it had one headlight out, no big deal, just a burned out bulb. We picked one up, then turned the lights on to make sure we were replacing the correct bulb, and now the one that was dead is the only one that works. Turn off, then back on and we're back to just having the original one dead. Wiggle the connector plugged into that one and all 4 headlights light up.
I followed him home from buying it, and his passenger side brake light also only works sometimes. He just left me a Voice Mail saying he has NO headlights now. I suggested to him that he check out the grounding, but when he asked me where all to look, I wasn't sure. Can anyone tell me where to tell him it should be grounded? Also any other possible causes would be nice.

[Longhorn Man]

Germlins...fun stuff.
Unplug all the lights, and spray some electrical contact cleaner in there, and scrup with w wire brush. You can do the rear ones with a battery terminal cleaner.
I suspect it is from all of the di-electric grease installed over the years making a poor contact. In all reality, i tend to NOT use the stuff onless there is a good reason.
The ground should be on the rad core support behind the battery, and also another one on the drivers side in the same general location...by the voltage regulator.

[sneakysnake]

Check all connections,grounds and bulb contacts,headlights, replace the dimmer switch.

[Longhorn Man]

snake, the dimmer switch would not cause the problem at hand.
There is only 3 wires on the dimmer..one hot from the switch (assuming the switch is turned on) and one wire to the high beams, then one wire to the low beams. The single wire seperates to two later on town the line on the core support.
There is a slim possibility of there being cuts in the wires and corrosion, however the chance is very slim.
There is also a chance of needing 2 headlights...intermitant fault...seen it a few times...but NEVER in 2 headlights on the same vehicle at the same time.

[Tynee]

Well, the possibility of needing 2 headlights seems even more remote when you figure that I went from 3 lights working and 1 not to the 3 working and the 1 not, then all 4 not working. That would mean intemittent faults on all 4 headlights. If that is the case it is time to start playng the Lottery!

[chickenwing]

A trick I learned in the Air Force: Once you find and clean the grounds (file/sand the terminal and where it contacts the frame), Bolt the ground back on and then blob coat the hole ring terminal/bolt head with rtv. Prevents corrosion from starting back up.

[Longhorn Man]

Or just paint over the terminal and surrounding area. If it is clean enough, and you don't mess with it...it'll stay clean for ever-ish.

[70 shorty]

You need to just turn the lights switch to the on position, not the intermittent position. (Sorry couldn't resist that one).

[Longhorn Man]

lol!

[Tynee]

lol. Thanks for the input guys.

[Mudder]

I went through that crap for a while. Going down a blacktop with no shoulders, no moon and poof out go the lights............... Not a fun ride. Never did fugure them out, but they have been ok for several years now.

[GreyHoundSteve]

I had this same problem when i bought my 67 and after looking at the rats next wire harness and the extent of the damage the po had done to it i decided to rewire my truck with a new painless harness.

I would first try to locate the problem which is probably a switch or the ground but if you see a bunch of bare wire like i did ...... i would replace the harness.

[Tynee]

We finally got time to chase it last night. As suspected every electical connection on the truck is covered in dielectric grease. Ever notice how much it looks like ear wax when its full of dirt? Anyway, after checking all the grounds, then taking them apart and cleaning them up just in case, started at the HL connector checking for voltage. None there, so worked my way back. Only had 1.5V on the blue wire at the dimmer switch. Checked the wiring diagram to see where that blue wire came from, HL switch. Quick trip to O'reilly's before they closed and $11 later he can drive after dark again. Ain't life grand?

[mrein3]

Originally Posted by Tynee

We finally got time to chase it last night. As suspected every electical connection on the truck is covered in dielectric grease. Ever notice how much it looks like ear wax when its full of dirt? Anyway, after checking all the grounds, then taking them apart and cleaning them up just in case, started at the HL connector checking for voltage. None there, so worked my way back. Only had 1.5V on the blue wire at the dimmer switch. Checked the wiring diagram to see where that blue wire came from, HL switch. Quick trip to O'reilly's before they closed and $11 later he can drive after dark again. Ain't life grand?

Now go and buy two relays, a spool each of red and black 10 gauge wire, and some type 56 connectors and make that new head light switch a relay controller. Your friend will never have to replace that switch again AND your headlights will have more voltage which equals more light.

[Longhorn Man]

This is a very worth while upgrade. I have everything sittin on my tool box ready to wire up. Probably this weekend I'll be doin that once I get the brakes done.