Hi,

I’m having a common problem, it seems…. Both brake lights don’t work on my ‘87 740GLE, even though the headlight tail lights, blinkers, hazard and back up lights all work. I’ve checked the fuse and the bulbs and even ohm’d out the brake switch (which it tested out OK). Since there is no voltage present at the brake light socket, I suspect it is the “bulb failure sensor” (which is really a relay, I’ve read). Thanks to all the people who have posted information that leads me to that conclusion.

But the darn thing is expensive… anywhere from 113 dollars locally, to a low of 50 bucks via an internet site ($20 for a used one, at one place). So I might try to fix/re-solder it, if I can determine that it is FOR SURE bad! Has anyone ohm’d out the round, 13-pin version of this bulb failure sensor/relay? I’m curious what the ohmeter readings should be from pin to pin, when the relay is good. I realize that there will be about 91 pin to pin readings possible, if I calculate that correctly. But most will be a reading of infinite or zero, except for the coil reading...

I’ll check all the contacts on the tail light assemblies, of course, but since no voltage is present when the brake pedal is depressed, I doubt that is the problem.

If anyone has such info about resistance readings for this sensor/relay, I’d appreciate it. Send it to wq2121@centralpets.com, if you can, and/or post it here for everyone to see.

I wish a parts place would take back an electrical part unused, but it seems they all charge a restocking fee on electrical parts, which I can understand. If it wasn’t so expensive, I wouldn’t hesitate to buy one, but funds are a little low at this point!

Have a great one….