Good evening all. Let me begin by stating that I have had zero time to diagnose this problem, but plan to do some diagnosing in the morning. I’m just looking for somewhere to start looking.
Anyway, the problem is this: I was driving home just a few minutes ago when my headlights flickered and then cut out for a few seconds. They came back on, but I hadn’t driven another 1/2 mile when they flickered again and went off for a further few seconds. This was repeated once more about a mile later, though when I pulled over (first time I was able to do so), they stayed off til after I restarted the car and banged on the dashboard.
Further symptoms: running lights, brake lights, and tail lights seem unaffected. Turning the switch for the headlights off and back on does not affect the issue.
Check the connector at the bulb. The heat from 25 years of use can degrade the connector and cause your symptoms. Replacements can be found at the parts store in the electrical aisle.
If both headlights went out at the same time I would look for maybe a relay or even the switch itself since both lights would have them in common.
PvtPublic - that’s what I was just thinking. Also, something I forgot to mention last night - when the lights went out, the highbeam indicator light on the dashboard went out, too.
You have a couple relays in line. The headlight relay and the step relay. Of course there is the headlight switch and the ignition switch. Since the engine did not die I would think the ignition switch is fine.
Headlight relays on 240s are prone to fail after a couple of decades of use. The later ones with the relay under the hood are worse because they corrode more.
To find it, click the headlights from high to low beam and follow the clicking sound.
Another thing that fails is the bulb-out sensor under the dash. Probably an orange can-shaped object about 1 1/2" diameter and 2 1/2" long. It has separate circuits for the low beam headlights, parking lights, and brake lights so the circuits fail one at a time. That sensor is expensive. When I lost the low beams on my '91, I found the wires that powered my low beams, cut them off the buib-out sensor plug, and wired them together with a big wire nut, bypassing the sensor. It was three wires (one incoming and two outgoing), gray, as I recall. The high beam wires do not go through the sensor.
One other suspect is the dimmer switch. I had the same problem on a 1978 Oldsmobile and it was a dimmer switch that was failing.