91 240 wagon - bizarre electrical problems

e777 · Post by **e777** » 23 Oct 2021, 13:46

The issue I am about to describe is the latest chapter in some struggles I have had getting the brake lights to work properly, (I did manage to fix the brakelights...until they unfixed themselves some days later

)

Anyway, here is what I am now dealing with (a real gem of an electrical problem).

- The headlight switch has three positions, off - running lights - head/tail lights

- When I turn the switch to the middle position, the overdrive arrow illuminates as does the defroster switch (!!)

- When I turn the switch to the third position, the overdrive light and defroster switch turn off

- This may or may not be connected to the ongoing issue of my brake lights remaining illuminated after my foot is off the brake and until the ignition is turned off (Turn the car on again, no brake lights illuminated until you tap the pedal again, and the same loop continues ad infinitum).

- The bulb failure relay is good (it works properly in my other 240)

- The brake light switch is new and functions properly (tested it in my other 240)

- This car is all stock. There is no funky custom wiring, spliced wires, etc.

II realize this could be ignition-switch related, but I hope to rule out the easier fixes first.

Thanks in advance for any advice you might be able to offer!

Post by **volvolugnut** » 23 Oct 2021, 13:54

Have you seen any evidence of the dreaded biodegrading wire harness on this Volvo? I think Volvo changed the wiring insulation by 199, but it still may occur.
If you are not familiar with this problem, The wire insulation crumbles away until wires in a common harness short to other wires. Weird lighting effects come and go until the car may not run until the harness is replaced.
volvolugnut

e777 · Post by **e777** » 23 Oct 2021, 13:59

Ah, OK, I will check that, although I have seen no signs of crumbling. I thought this was mostly an issue from 86-88. Then again, with a car this age, even a good harness can be compromised. I will check it out.

Post by **volvolugnut** » 23 Oct 2021, 14:16

Look at hot areas like near headlights and over the engine. Also where exposed to the sun.
volvolugnut

Post by **volvolugnut** » 23 Oct 2021, 14:29

Have you checked the condition of the wiring near the headlight switch? It appears the position of this switch impacts other random things they should not.
volvolugnut

e777 · Post by **e777** » 23 Oct 2021, 14:37

Yes, will do. I looked at the light switch wires recently and they looked fine. But I will follow them down farther to see what's there, if anything.