Headlight going on and off - Impala Tech
Electrical & Wiring Troubleshooting electrical problems

  • 1 Post By Steveman
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post #1 of 6 (permalink) Old 08-24-2018, 10:20 PM Thread Starter
Join Date: Nov 2017
Location: SE PA
Posts: 28
Headlight going on and off

Long story short, we finally got our 1968 impala on the road. But recently the headlights will turn off for 5 or 6 seconds then briefly turn back on and then right off again. I replaced the headlight switching dash panel a few months ago and lights worked fine. This has new motor/trans and has good ground from battery to intake, intake to body and body to frame. The ground lug behind battery has been cleaned, and tonight just cleaned ground lug behind driver side headlight and replaced the floor dimmer switch. I have been reading about replacing the voltage regulator ( external).

Does anyone have any ideas on what to look for

FYI itÂ’s been driving for a few months and did not have any issues, my son told me about a month ago that lights were acting up but he stated tonight that this is way worse than when it happened back then.


1968 4 dr Impala
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post #2 of 6 (permalink) Old 08-24-2018, 11:05 PM
Join Date: Jan 2006
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Could be in the light switch, the dimmer switch, the wiring, wiring termination and/or connectors, in the head light bulbs, in any of the grounding points that are supposed to be in place, or in your battery cable ends.

Big Dave
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post #3 of 6 (permalink) Old 08-25-2018, 12:00 AM Thread Starter
Join Date: Nov 2017
Location: SE PA
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Just to add to story, we did have exhaust installed/welded. Would this cause an issue.

And this is isolated to the headlight circuit. Marker lights and tail lights stay on and are un effected.

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1968 4 dr Impala
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post #4 of 6 (permalink) Old 08-25-2018, 11:35 AM
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Electrical points burn with use. In these early cars they didn't use relays to handle the heavy electrical loads at the switch so they generally burned up after a few years of constant use (if you never drove at night or in fog or rain they lasted longer). The factory coated their points with tungsten to allow them to last longer. The Chinese importers don't do that as it adds cost that they would rather keep as profit. In this regard an AC-Delco branded light switch (assuming it isn't counterfeited) would get you a better quality part.

The other switch in the circuit is on the floor where it is exposed to not only high amperage switching, but dirt, grime and water. It isn't used as much (some like my wife, never use high beams) so it may have died years ago, and you wouldn't know it until you used it for the first time. Then it fails miserably, because the springs that maintain contact between the points have rusted away.

There is a chance that if only one bulb is flickering it could be a broken filament that touches intermittently to burn when in contact and flash out when not touching. Chances of both doing that simultaneously are slim.

Finally your wiring was suspect the day they built the car. The days of finding copper ore lying on top of the ground are long gone. Deep hard rock mining, or huge open pits that are up to a mile and half deep are used to expose copper ore which makes copper a very expensive metal after WWII (the reason the factory uses aluminum in their radiators today). The factory used the bare minimum length to reach, and then undersized the wire for the load when they built your car new. Add a half century to stiffen the experimental PCV insulation used on the wires, and oxidize the copper strands and you can see why it is suspect. Vibration and movement due to rotted rubber insulators and you get broken wires and wires pulled out of terminators.

Most mechanics will not touch electrical problems because they are so time consuming: it isn't worth their while. There are specialty shops that work only on automotive and marine electrical problems, but they generally spend their time, and your money, by replacing all of the wiring with a new wiring harness and replacing all of the switches.

Here is a hobbiest version of a professional probe that I use in conjunction with a twenty five foot ground wire to find automotive electrical faults:


Big Dave
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post #5 of 6 (permalink) Old 09-07-2018, 05:11 AM
Join Date: Nov 2016
Location: Palmerston North New Zealand
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Not sure if you've managed to fix this yet, but I had a similar problem due to having aftermarket halogen bulbs in the high beam lights. After about 20 mins they would go out and only come back on after a short wait. Realised after a bit of Googling that the lights are designed to do this if the circuit overheats, instead of blowing a fuse. This way you can wait a bit and still have headlights for a short while, rather than nothing at all. Seems my 50 year old wiring wasn't up the task of halogen bulbs.

I fixed the problem by connecting a couple of relays into the circuit (one for low beam one for high) and fed them directly from the battery. Then the headlight switch only acts as a switch instead of having all the power running through it. Google headlight relay and there's a couple of good step by steps. I installed the relays in the old regulator housing so the install is all hidden. Upgraded the wiring gauge from the relays to the headlights as well for extra safety.

End of the day, the lights are way brighter, the wiring doesn't get hot, and I can upgrade to full halogens if I want. Might help in this case maybe?
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post #6 of 6 (permalink) Old 09-07-2018, 04:07 PM
Join Date: Aug 2008
Location: Miamisburg, Oh.
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Good suggestions above.

You mentioned replacing the 'headlight switch' but I assume you mean the one on the dash.

Did you replace the dimmer down by your foot? Those wires and connection can get a bit corroded. Lots of folks have had to replace the dimmer switch.

Also, I'd have no concerns about the dual exhaust work. No correlation there.

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