Volvo RWD 200 Forum

The right side (passenger)brake light was not working. Brake bulb and connections at rear light assembly check OK. Traced wiring to Bulb Failure Warning Switch (BFWS) and checked the pins with a test light. Pin 11 (right brake) was not working with pedal depressed. I had another (same part #)used BFWS handy so I swapped them. Now all 3 brake lights work. But wait, there's more -
When I turn on the tail lights, the 2 brake lights illuminate along with the tail lights without pressing the brake pedal. Pressing the bake pedal only illuminates the 3rd brake light. Same when I turn the headlights "on". So, thinking it was the replacement BFWS, I swapped it back to the original and get no right brake light (as before), however, when I turn on the tail lights, the same symptoms prevail: both tail lights illuminate with both brake lights "on". This makes me think the issue is not with either of the BFWSs. So, I again replaced the original BFWS with the spare. Now at least I get 3 brake lights when I press the brake pedal, however when I turn on the tail lights, I get both tail lights "on" and brake lights "on" all the time. Pressing the brake pedal only lights the 3rd brake light when tail(&brake) lights are "on".
Is it the BWFS or could it be another separate problem? Any advise is appreciated.
Thanks -
Marc
1990 240 148K