Headlights turn off while driving

MustangMatt1966 · Apr 20, 2006

Hey guys, i have a little problem. When i have been driving my car for about 10 to 15 mins at night, the headlights begin to turn on and off and eventually turn off. At first i thought that after running for a while, the lights were loosing voltage. Then i thought that maybe the switch is overheating or something. But i need an answer cuz it is going to be just my luck im driving and a cop sees me as my lights are going on and off.. please help

86bluecobra · Apr 20, 2006

either the switch is overheating or the relay is. i have heard of this problem when peeps put larger lights (brighter more watts) then the system was designed for.

thehueypilot · Apr 20, 2006

This happened on my car when I switched to halogen head lights. In my case it was the dimmer switch over heating and opening the circuit causing the lights to go off. The best fix is a Painless wiring harness made to run the head lights off a relay to reduce the amperage through your switches.

66HertzClone · Apr 20, 2006

There is no fuse for the headlights, the light switch has a built in circuit breaker. They can act up when they get old and these switches are relatively inexpensive and easy to replace.

Before re-wiring the entire system, replace the switch. As said above the dimmer switch may be causing a short. It can be removed and checked or even replaced as well.

krash kendall · Apr 20, 2006

A new headlight switch is cheap. I had the same problem a while back and that fixed it.

1320stang · Apr 20, 2006

Replace the headlight switch if you have original styled headlights. If you've gone to the new headlights everyone puts in, you'll need to change the power for them over to a relay AND you may need a new headlight and/or dimmer switch.

CochinoFilipino · Apr 20, 2006

krash kendall said:
A new headlight switch is cheap. I had the same problem a while back and that fixed it.

Same here. A new headlight switch is all that I needed to fix mine.

Installing relays is a nice upgrade and something you should look into.

MustangMatt1966 · Apr 20, 2006

i do not have upgraded lights. so we can rule that out, what switch are we talking about, the switch on the floor from high beam to low beam or the dimmer switch on the dash...sorry for the dumb question

mustangdave · Apr 20, 2006

The headlight switch on the dash.

evilfitz · Apr 20, 2006

The other guys are probably right, but when I bought my car and was driving it home the lights we're flicking on and off. It turned out my alternator was on its last legs or already dead. Once I swapped that out they've never done it since. That's with a stock electrical system in a basically stock car. The car started and ran fine up until the battery died out.

MustangMatt1966 · Apr 20, 2006

evilfitz said:
The other guys are probably right, but when I bought my car and was driving it home the lights we're flicking on and off. It turned out my alternator was on its last legs or already dead. Once I swapped that out they've never done it since. That's with a stock electrical system in a basically stock car. The car started and ran fine up until the battery died out.

i have the powermaster 100 alternator, one wire hookup, i know it has enough volts, but im worried about the wiring...i just dont know what to do..i dont want to spend 500 on a painless kit.....ugh

67chad · Apr 20, 2006

Trust what they are all saying it’s most likely the dimmer switch. I had the same problem years back, when you see them go out reach down and feel the light switch it should be hot to the touch. Call up your favorit classic mustang supplier and get one they are not vary expensive. There should be no need for relays or a new wiring harness but they would also be a benefit to your 40yr. old car.

MustangMatt1966 · Apr 21, 2006

67chad said:
Trust what they are all saying it’s most likely the dimmer switch. I had the same problem years back, when you see them go out reach down and feel the light switch it should be hot to the touch. Call up your favorit classic mustang supplier and get one they are not vary expensive. There should be no need for relays or a new wiring harness but they would also be a benefit to your 40yr. old car.

thank you

Flyin'Fastback · Apr 22, 2006

MustangMatt1966 said:
i have the powermaster 100 alternator, one wire hookup, i know it has enough volts, but im worried about the wiring...i just dont know what to do..i dont want to spend 500 on a painless kit.....ugh

The Painless wiring harness that you need is not the complete rig, just the H4 halogen headlight conversion harness. It runs about $75-$80. Neat design, too - one end has a coupling that you plug into the factory harness in place of one of the headlights. The new harness, relays and all, taps into a 12v source and has the appropriate heavy wiring for the extra current demands of overwattage bulbs. It's a worthwhile upgrade, even if you keep the old sealed beams. With good halogens (such as E-Code Hellas), you'll see a remarkable difference.

BTW, the '69 Mustang had a heavier-duty circuit breaker in its headlight switch (that was the year with quad headlights). A '69 switch is a good idea if you'd prefer not to mess with relays. You'll have to switch the mount bracket and pull knob, but otherwise the switches are interchangeable.

MustangMatt1966 · Apr 23, 2006

[/QUOTE]
BTW, the '69 Mustang had a heavier-duty circuit breaker in its headlight switch (that was the year with quad headlights). A '69 switch is a good idea if you'd prefer not to mess with relays. You'll have to switch the mount bracket and pull knob, but otherwise the switches are interchangeable.[/QUOTE]

thanks so much, I am going to order the 69 headlight swith, to handle more amps..i think part of the reason, is that i have my tach light connected off the headlight wire, so when i turn the lights on, the tach light comes on, and i think its drawing from the amps to the light..is that possible??

dennis112 · Apr 23, 2006

i think part of the reason, is that i have my tach light connected off the headlight wire, so when i turn the lights on, the tach light comes on, and i think its drawing from the amps to the light..is that possible??

Tach light amp draw is negligible.

MustangMatt1966 · Apr 23, 2006

dennis112 said:
Tach light amp draw is negligible.

ok then the switch might just be going

dennis112 · Apr 23, 2006

MustangMatt1966 said:
ok then the switch might just be going

That would be my first guess--I've had it happen to me too.

MustangMatt1966 · Apr 23, 2006

View attachment 474711

just to clear things up, we are talking about this swtich correct (highlighted in green) thanks, Matt

krash kendall · Apr 23, 2006

Headlights turn off while driving

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