Headlights go on and off when engine is hot

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340cudaman1

340cudaman1

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Went to a cruse-in on a hot night. Stuck in traffic for about an hour. When I left it was dark. When I was about 5 mins from home the headlights kept going on and off. The dash switch may be the problem (dash lights don't dim properly, ordered a new 1) however could it be the headlight relay or another problem? All the other lights work, tail lights, parking and turn signals (they don't go on and off).
 
Could be the switch, the wires or the dimmer switch on the floor.
These old girls didn't have headlight relays.

Might want to turn them on just sitting and do a wiggle test on everything before buying anything besides the dash switch.
 
The headlight switch does have built in protection that will cause exactly what you describe but...
If the headlight switch itself is the fault, it would occur without engine running. Put a good battery charger or jumper cables from another vehicle on and turn the lights on.
 
Do you have a bare wire making a short somewhere. Like bouncing and hitting on and off. Or a bad ground.
 
had the exact same damn thing happen to me. the headlight connector roasted the black w/ red tracer power in wire. get the old melted piece out, soldered in a new brass connector, shazaam! lifes good! hopefully your issue is something that easy. good luck!
 
RedFish said:
The headlight switch does have built in protection that will cause exactly what you describe but...
If the headlight switch itself is the fault, it would occur without engine running. Put a good battery charger or jumper cables from another vehicle on and turn the lights on.
Click to expand...

I was thinking along the same lines myself, that it maybe the thermal trip in the light switch.
We have this issue quite a lot with 60s US cars here in Germany. German traffic regulations require sealed beams to be removed & H4 headlights to be fitted. Due to the increased wattage of the H4s, more current has to flow, thus tripping the thermal protection in the light switch. We fit 2 relays in the headlight circuitry. 1 for dipped beam & 1 for high beam. Problem solved.
 
If the terminals are getting hot and melting the connector/insulator, why?

I'd find the issue causing the problem. Melted connectors are a symptom.

Relays are a great solution to the headlight performance and switch issue. Part of the reason I started building kits.
 
crackedback said:
If the terminals are getting hot and melting the connector/insulator, why?

I'd find the issue causing the problem. Melted connectors are a symptom.

Relays are a great solution to the headlight performance and switch issue. Part of the reason I started building kits.
Click to expand...

^^^yes I agree. apologies, I forgot to mention the headlight switch was original too, and it was reeealy crusty. had high resistance throughout the internal contacts....as we all know, resistance creates heat.....I installed a new switch the same time I fixed the connector.
 
My first thought. However I replaced the regulator as it wasn't charging correctly and the lights did the same thing, regulator works ok now but lights still going on and off. Just got the new dimmer switch this afternoon, have to install it in the dash. Hope that is the problem. I do have a spare hibeam foot switch, if the dimmer doesn't solve the problem I'll replace the foot switch also.
 
66durgederp said:
^^^yes I agree. apologies, I forgot to mention the headlight switch was original too, and it was reeealy crusty. had high resistance throughout the internal contacts....as we all know, resistance creates heat.....I installed a new switch the same time I fixed the connector.
Click to expand...

All good.

The stock wiring is marginal at best, voltage drop is pretty big factory in performance.

That gif in your sig makes me laugh. My ex-gf would do something similar. LOL
 
340cudaman1 said:
Went to a cruse-in on a hot night. Stuck in traffic for about an hour. When I left it was dark. When I was about 5 mins from home the headlights kept going on and off. The dash switch may be the problem (dash lights don't dim properly, ordered a new 1) however could it be the headlight relay or another problem? All the other lights work, tail lights, parking and turn signals (they don't go on and off).
Click to expand...

have seen the dimmer switch do this several times. I would start by replacing it
 
I replaced the dash light switch today. I hope that solves the problem. Now my dash lights up better too.

I want to THANK ALL OF YOU for your help.
 
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