Strange Headlight problem

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FastMatt

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This problem has me confused. My 1972 Demon when you first start the car you can turn on the headlight and use the foot dimmer switch to toggle back and forth from lo to high beams. Now after you drive the car for a wile at night all of a sudden with out touching the dimmer switch the red “high beam” indicator in the dash will light up. Not as bright as when you click it normally but lit up. Once that happens the dimmer switch will no longer do anything you press it and the light just stays on and you can no longer get the headlights to toggle back and forth between high and low. I tried replacing the dimmer switch and I replaced the main light switch also and it did not change a thing. Only way to get it to go back to working is to shut the car totally off then restart it and they start working like normal again till it happen again after driving for a 10 min or so.

Has anybody had this problem? If so how dod you fix it?

Thanks
 
no but it sounds like a short in the floor switch connector or wires

check the plastic connector body (3way) has not melted and is allowing one of the 3 contacts to hit the metal "heavy foot" protector edge on the square switch body/mount
 
A lot of weird things can happen when you lose a ground. Sounds like the power to your headlights is finding a ground through the high beam indicator light. I would check the grounds on your headlights.
 
Need to look at how the car is optioned. Could be an atypical item such as the headlight warning light/chime that relates to the key switch.

I say this because the basic headlight system does not involve the key switch. Headlights and the parking lights and the instrument lights all can be powered with the key off. Since the problem occurs with key on, and goes away with key off, it must be related to the key switch or a cross wire short to circuits turned on by the key switch.

Main circuits for a '72 (w/ a standard alternator, and points ignition)
1724156528205.png
 
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Headlight switch is a multi-function switch with several feeds in. None require the key switch. The connection at B1 is the one for the headlights and has a 15 amp circuit breaker internal to the switch.
1724156979124.png
 
something is getting hot, likely the dimmer switch. If you unplug at the dimmer, does the high beam light stay illuminated? If it doesn't, you know the issue is from dimmer switch/downstream from there.

Getting the load off that stuff like one of my relay kits would likely solve the heat/light issue.
 
crackedback said:
something is getting hot, likely the dimmer switch. If you unplug at the dimmer, does the high beam light stay illuminated? If it doesn't, you know the issue is from dimmer switch/downstream from there.

Getting the load off that stuff like one of my relay kits would likely solve the heat/light issue.
Click to expand...
How do I go about ordering one of your kits?
 
If you unplug the dimmer foot switch, doesn’t that disconnect power to both the high and the low beam headlights?
 
When my headlights were acting up, it was the dimmer. Local parts stores should still carry it, just replaced mine 2 years ago. Not saying that it can not be something else, inexpensive part and easy to replace.
 
Aren't the filaments supposed to touch each other? When they don't, you replace them.
 
CRUZE 418 said:
Aren't the filaments supposed to touch each other? When they don't, you replace them.
Click to expand...
Well my car only has one headlight per side, so inside are two filaments, one each for hi and for low. They ate shifted slightly as to focal length, giving differing patterns down the road. They are NEVER both on at the same time. If the non running High filament droops onto the running low, it will turn on the hi-beam lite, This occasionally happens when the high beam filament gets hot and melts. This makes it confusing, cuz you already know, that Hi-beam doesn't work.
However
I have no idea how the hi-beam lite can come and go, that's a new one.
Ima thinking the foot-switch has an internal problem. I would just stomp on it a buncha times and see what happens.
 
AJ/FormS said:
Well my car only has one headlight per side, so inside are two filaments, one each for hi and for low. They ate shifted slightly as to focal length, giving differing patterns down the road. They are NEVER both on at the same time. If the non running High filament droops onto the running low, it will turn on the hi-beam lite, This occasionally happens when the high beam filament gets hot and melts. This makes it confusing, cuz you already know, that Hi-beam doesn't work.
However
I have no idea how the hi-beam lite can come and go, that's a new one.
Ima thinking the foot-switch has an internal problem. I would just stomp on it a buncha times and see what happens.
Click to expand...

I have replaced both the foot switch and the main light switch and it changed nothing. I have a crackedback headlight wiring kit coming, and I think I may try changing the head lights too now that you mention that.
 
I think the crackedback headlight harness is a great idea, but you may want to find your problem first before changing a bunch of stuff. That usually just makes trouble shooting harder.
 
Simple to check out one other thing. When the issue arises, Unplug the headlights one at a time, see if it resolves. That should identify whether the headlights are an issue with filaments touching.
 
Mike69cuda said:
If you unplug the dimmer foot switch, doesn’t that disconnect power to both the high and the low beam headlights?
Click to expand...
It's a technique/approach to identify where the electrical issue may lie.
 
Murray said:
Headlight grounds are on the radiator support.
Click to expand...

AJ/FormS said:
Yes, one of the filaments was touching the other. I replaced the bulb
Click to expand...

FastMatt said:
I have replaced both the foot switch and the main light switch and it changed nothing. I have a crackedback headlight wiring kit coming, and I think I may try changing the head lights too now that you mention that.
Click to expand...

Think about this guys.
If a high beam bulb filament is being used as a ground path it could cause the high beam indicator to be lit.

I’ll place my money on a ground issue at the radiator support if it’s not actually a filament, but I believe a filament touching would cause the indicator on the dash would be normal brightness.
Ground failures are notorious for dimmer than normal lighting.
 
AJ/FormS said:
Yes, one of the filaments was touching the other. I replaced the bulb
Click to expand...

Changing the head lights seems to have fixed it.

I'm still going to install the headlight Harness once it gets here.

Thanks everyone for all the ideas to look at.
 
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