flashing headlights

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Oct 2, 2011 | 04:22 AM

75styleside

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flashing headlights

so i was driving my truck and about after an hour my headlights started flashing on and off. all my other lights stayed on, its intermitent and only lasts for a min or so my battery is good my alt is good did a wiggle test on all the wires under the dash and behind the headlights while sitting on the side of the road at night. just thought i would see if anyone else has seen or had this problem?

Oct 2, 2011 | 06:12 AM

jim collins

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From: South west Idaho

Bad ground someplace maybe ,that's the most common problem with lighting.

..JIM

Oct 2, 2011 | 06:20 AM

moparmusclecars

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I agree, you most likely have a bad ground.

Oct 2, 2011 | 07:48 AM

mikeo0o0o0

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From: Stanley, VA

It could also be the switch itself or an intermittent short.
Headlight switches have a circuit breaker built into them. When it trips it resets automatically in a few seconds.
My guess would be either an intermittent short is causing it to trip then reset or the switch itself is bad. When they go bad, switches can get hot causing the breaker to trip and reset.

Oct 2, 2011 | 08:39 AM

dlburch

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From: Kansas

in addition to the above suggestions, the dimmer switch could also be going bad.

Oct 2, 2011 | 08:47 AM

HIO Silver

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From: NorCal

Quote:

Originally Posted by mikeo0o0o0

2x with Mike... the headlights' current runs through the switch. As electrical systems age, they tend to draw more current which leads to more heat. One way to solve the problem is to unload the light switch and install dedicated relays for the headlights. Generally, you'll end up with brighter lights too.

Oct 2, 2011 | 10:56 AM

ctubutis

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From: Denver Metro Area, CO

I would also be suspecting one of the switches - headlight switch, dimmer switch.

The factory headlight wiring systems are famous for a tan/white wire melting at the dash switch.

Lots of guys in 80-86 have either made or purchased from LMC a wiring harness that uses the dash switch to actuate relays which then go supply power to the headlights. This keeps all that current out of the cab wiring, and people claim they get brighter headlights.

The online version of LMC's 73-79 catalog seems to kinda suck, things aren't listed where the text says they are but here are two pages of that catalog with the harness I described (Item #47-3660):

LMC Truck Parts - Page 149
LMC Truck Parts - Page 70