I have an 89' 740 GL. I was wondering if anyone could tell me if there is a relay that controls the brake lights, and if so where I could find it. The problem that I am having is that only my 3rd brake light works (the one in the rear window). The regular brake lights will not work. All other lights seem to work fine and I have checked all the fuses and bulbs. If anyone has any advice I would greatly appreciate it.
Thanks, Charles
Sounds like either a bad ground or the bulb failure warning sensor.If you get no power to the connector on the taillight then it is the sensor. It's round, orange,and located behind the ash tray. Pull out the ash tray, pop off the bezel around the lighter, remove the two screws there and take out the pocket.Try to find some one who will let you borrow theirs to try before you buy because they are expensive.
There isn't a relay, I've fixed a couple of these with the same problems with the taillights by resoldering the circuit boards in the bulb failure sensor, it's a red can near the relays.
If you change the bulb failure warning unit you should restore normal operation of all three brake lights. The thing to change is the round can at left of third row of relays in the relay tray. You could try to see if there is any corrosion around the connections before discarding the old unit just in case this is the cause of the trouble.
Cheers, Peter. .
Have something to add? Share your thoughts — no account required.
Ask the community — no account required