Hi everyone. I know this subject has been covered extensively, but I haven’t quite seen an answer to what’s going on with my brick. I have a 1991 240 with 170K miles. I can’t get the passenger side brake light to properly light when the other lights are on. What I mean is, when the headlight switch is off and I press the brake pedal, both brake lights properly light nice and bright. If I turn the headlight switch to the center (for parking lights) and press the brake pedal, only the third and driver’s side brake lights properly light. The one on the passenger side only blinks out for a split second and returns to its lower or standby glow, if you will. It’s almost as if it wants to light but can’t for some reason. It behaves the same way if the headlight switch it turned to headlights on, it just blinks.

This is what I’ve done so far:

1. Installed a brand new circuit board.
2. Installed new bulbs to be sure everything matched.
3. I’ve got about 4 bulb failure relays that I have tried, still with no change (I must admit they have all come from junk yards but I figure one at least has to work).
4. Cleaned the bulb socket contacts and swapped sockets and bulbs from left to right.
5. Cleaned the circuit board ground wire. Still no change.

I read that maybe the taillight harness may have corroded connections and may be grounding against some other wire. If so, where does the passenger side taillight wiring harness connect? I hope this doesn’t amount to beating a dead horse, but I’d really appreciate some help. Thanks everyone.

 

For those of you interested, I’ve resolved the blinking brake light issue. I simply swapped socket brands/manufacturers. The new circuit board I installed recently was an aftermarket Alvo brand. I had an Alvo brand brake light socket on hand and thought it might make a difference. I removed the Volvo socket and installed the Alvo socket and viola… the brake lights work as they should. I don’t know why it worked, I just know it did. There was probably something wrong with the other socket that I just don't see. So, if anyone else is having quirky issues with their lights, give a brand swap a shot. It just might get you somewhere.