Headlight gremlins Options

[john77]

My headlights have decided to randomly turn themselves on and off as I drive, which is a lot of fun at night on the I405 as drivers think some obnoxious d*ck is flashing them.

I cleaned up the grounds and all the ground wire connectors by both headlights but it’s still happening.

Could this be relay connected, or are they more a once dead completely dead kind of deal?

I thought i’d ask before I drop $20 on a new one.

For the record, I have those sealed GE led headlights, and it’s happening simultaneously to both, so I know it’s not the bulbs.

[john77]

I took the car out last night. Still no conclusive answer.

Warming up on my driveway, lights on, they work fine. 10 minutes sitting there, not a glitch.

I drove 20 feet down the street and they cut out. I tried waggling the switch, nothing.

I turn them off and back on and the lights either come straight back on (and then die) or they flip up, nothing for about 10 seconds, then they come back on, then they die.

Is waggling the switch supposed to have some effect if it’s the switch?

[lierofox]

I took the car out last night. Still no conclusive answer.

Warming up on my driveway, lights on, they work fine. 10 minutes sitting there, not a glitch.

I drove 20 feet down the street and they cut out. I tried waggling the switch, nothing.

I turn them off and back on and the lights either come straight back on (and then die) or they flip up, nothing for about 10 seconds, then they come back on, then they die.

Is waggling the switch supposed to have some effect if it’s the switch?

Looking over the wiring diagram there's a few possible candidates for a single-point-of-failure for the headlights.

From the ignition switch: Terminal X feeds power to a separate wire that leads over to...
The headlight switch: When pulled to position 2, power is supplied from input terminal 15 to output terminal 56. From there it heads over to...
The Dimmer Relay: Power comes in on terminal 56, and outputs to either the low beam terminal (56a) or the high beam terminal (F) and both lead over to...
The fuse panel: The low beam wire feeds to fuse terminal 4, which is always jumpered to fuse terminal 3, the high beam wire feeds to fuse terminal 2, which is always jumpered to fuse terminal 1.

At this point all 4 functions have split off to separate wires (low left, low right, high left, high right.)

If your low beams die, but you hit your dimmer lever and get high beams, I would inspect the wire between Fuse 4 and the dimmer relay. If those look good and solid I would condemn the dimmer relay.

If your low beams die, and your dimmer lever doesn't give you high beams, I would inspect between the dimmer relay terminal 56 and the headlight switch terminal 56 (if equipped, this terminal also supplies power to your fog light switch, terminal 15.)

Before condemning the headlight switch though, also inspect the power going to input terminal 15 on the headlight switch. If power is intermittent there, that means your ignition switch is suspect, try wiggling your key in the ignition and twisting it slightly, see if any sort of motion will cause your headlights to drop out without also killing the engine.

If your ignition switch seems fine, and no amount of wiggling it seems to set things right, you can try servicing the headlight switch. One of the failure points of the headlight switch is that the sliding contacts get worn/pitted, you can try disassembling it and inspecting the contacts and the springs that hold the contacts down. If excessively worn, I believe that 2 of the contacts are actually identical, and you can swap them around and reassemble the switch. (Not sure if this is the case for a '73 switch, it was true in my '75.)

From personal experience on my own 914, I've had problems with all 3! Replaced the ignition switch, serviced the headlight switch, and replaced the dimmer relay.