240 headlights malfunctioning
 

A million threads on the subject but couldn’t find an answer.

I’ve a 1982 242 DL, B20E and M45.

Problem being that headlights don’t turn on.
I pull the stalk and high beams light up but they don’t stay on. Turning the knob does turn on running lights and gives power to the blinkers when turning the stalk.
No abnormalities in the dash lights when I turn the knob to headlights on. The headlight relay seems to work when tested and just in case I bought another one from a wrecker.

The light broken light in the dash does turn on when the headlights are turned on.
I’m omw to get a probe from a friend so I can test the wires but until then I’ve got no more ideas


All help will be appreciated

Joni

Simply use your $5 test light or $10 voltmeter to check for power. When you turn the switch on power is sent to the headlamp relay. (under the hood, near the battery that clicks when flashing and changing high to low) That relay sends power to either the low or high beam filament.

The bulb out relay works by comparing the current used, left and right on 3 circuits. The low beam bulbs, the rear parking lights, and the brake lights.

For instance - if the bulb out light comes on with the light switch off (engine running) and you are stepping on the brake pedal - the left and right brake bulbs are not using equal amounts of current. One might be out, or a bad connection, or sometimes just 2 different brands of bulbs.

Bulb out light with brakes not applied - light switch in parking position - that's the left and right parking bulbs not using the same current.

Bulb out only with headlamps - that is the left and right low beam (only) using not the same current. Note if both left and right are out - (on any of those three lighting circuits) The bulb failure light will stay off - for the bulbs are using the same current , 0 amps.

I’ve been working at this for quite a while now and still can’t get it figured out.

I’ve dug around and if I’m correct this only has one headlight relay, i.e. the step relay or something. That aluminium one in the fender.

I’ve tested the fuses and the cabin switch, both are fine. The issue must lie between the relay and the lights if I’m reading the wiring diagram correctly. Or by some wicked chance both of my relays are faulty.

I have found and (almost) fixed the issue.
The yellow wire going to the headlight relay seems to be broken somewhere along the way as when I took a wire from the fuze to that the headlights work normally.

Problem solved

unless yours was replaced you are in the notorious biodegradeable wiring harness years range, so not unexpected you would run into such issues...

I believe '82 was prior to the biodegradable wiring. I thought it started in '84

That may be but then you are talking about a 40 year old wiring! Even if it wasn't the "biodegradable" kind, plastic does deteriorate after so many years.

dave barton says 80-87....

https://www.prancingmoose.com/volvoharnesses.html