# 68 headlights posessed by Old Nick



## echo6delta (Oct 13, 2008)

Hey y'all,
Just started getting under the hood of my GTO long enough to play with it some, but I had a problem crop up that I (and my Certified Gearhead™ buddies) can't diagnose.

I'm driving around at night, come to a curve that's notorious for deer. I hit the footswitch for highbeams, and the headlights WENT OUT. Which kinda sucked, because I had to use my flashers for a mile or so until I could park. 

Now, I'm NOT a skilled mech, and I'm a plain lousy troubleshooter. I know there are no fuses marked for headlights specifically, and I know I had just replaced the alternator two days prior. Then again, this was the first time in a while I'd been driving at night. I poked around under the hood, checked the voltage regulator and that other similar thingy (with three wires plugged into it) on the driver's side firewall for good connectivity. They checked out, so... I scratched my head, slammed the hood, and went inside to have beers.

Replaced the 1000/850 CCA battery the next day (because it was needed), but no change in headlight status.

Two days later, I was driving around running errands. Went inside to watch a ballgame and left the parking lights on for about 40 minutes or so - enough to make a dent in the battery. Got it jumped off, went straight to a shop and pulled the shiny new battery & placed it on a charger for an hour. While I waitied, I replaced the voltage regulator, just for S&G.

Put the fully-charged battery back in, and THE HEADLIGHTS WORKED. Holy smacks, I was happier than a pig in s*it!

Heading down the road back to the house, it's past twilight, and I'm coming to a curve that's notorious for deer, and... yes, I'm a dumbass. Hit the footswitch AGAIN, and the headlights died AGAIN. Replicated everything (including replacing the VR and charging the battery) the next day, in the same order, and could not get the headlights on.

Does anyone have an idea WTF this could be? I've checked what grounds I can find (without a shop manual), and they are good to go. Alternator, battery, VR, are all good. I don't think the switch itself is the problem, and my next step is getting a new wiring harness. That will be a big PITA for me, because I can barely even spell "multi-meter", much less use one.

Any thoughts? :confused


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## 05GTO (Oct 6, 2004)

On my 66 and 67 there is a ground wire on the headlight wire harness that connects to the core support and supplies ground to the headlights. Check that connection and the ground on the core support.


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## Too Many Projects (Nov 15, 2008)

Look for corroded wires at the dimmer switch plug and replace as necessary.


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## Gen410 (Dec 1, 2008)

Invest 15 bucks in a shop manual, maybe even one on a CD. Get a multi-meter, and take all that hideous electrical tape off of your wiring, and get new wiring from the front to back. That is 100% likely to be your problem. If its all original it's most likely to be corroding as stated above. Think of it as shoelaces... The more you use them, the thinner they are going to wear, and eventually will just snap, ya know? Keep us posted with the progress.


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## Rukee (Feb 8, 2007)

Check for battery + voltage at the headlights and for a ground curcit at the headlight plug. I'm betting it's either a ground problem or a dimmer switch problem.


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## Too Many Projects (Nov 15, 2008)

Rukee said:


> Check for battery + voltage at the headlights and for a ground circuit at the headlight plug. I'm betting it's either a ground problem or a dimmer switch problem.


Absolutely...........
ALL the power for the headlights goes thru that switch, low and high beams. When the terminals get corroded, it reduces the voltage and will lose contact completely. The switch will corrode internally and fail also. This is a quick, easy step to check.
Poor grounds at the headlight plugs will rarely cause all the headlights to go completely out. They will glow dimly or ground back thru the positive side and the high beams may glow on low beam.

It could possibly be the headlight switch too as the power to the dimmer comes thru that, but I would start at the dimmer.


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## echo6delta (Oct 13, 2008)

I didn't actually notice that ground hooked to the core support before; I'll be certain to look for it.

Gonna be swapping (temporarily) to a Holley 650 today, so in the midst of that I'll be sure to get at the dimmer switch, pull connections, and clean them thoroughly with Hoppe's gun solvent and a wire brush.

What? I'm a gun guy, too! It actually works pretty well!

I'll let y'all know how it goes. Thanks again for the tips. It's great to have a place to find multiple viewpoints on the same problem. :cool


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