Rear Sensor Light

"Rear Light" sensor light keeps coming on. But rear lights work find. I think its a bad sensor. Anyone have any ideas where the sensor is located. Also, anyone have any ideas what diagnostic test I can perform to see if the sensor has gone bad. I have a 1987 528e.

I'm betting it's a light and not the sensor. On my '89 E30 I could not clear a Brake Light failure on the Check panel. I replaced bulbs and even went so far as to remove the light check panel and the light sensor board. They both "looked OK" - a real technical diagnosis there.

After changing all the brake bulbs and reinstalling the sensor, the problem was still there. A day or two later, I was backing into a parking space in front of a storefront window and finally saw the source of the problem - it was the high-mounted center brake light that was burned out. I had forgotten about that one. One of the dangers of trouble shooting with the trunk lid up.

The sensor is looking at resistance readings which indicate the lamp filaments are still intact. It's possible (I guess) that a lamp could light and still have less than the minimum resistance but is should be visibly dimmer than it's sibling.

Not much help other than to be sure you, like me, haven't overlooked the obvious.

:smokin:

Even the wrong wattage bulb can set this light off, check the manual, ai think they are all 21 watt bulbs...