I have a 89 740 (UK)
I do like this sensor, but it can be a right pain.
The sensor works on the resistance of the filament of the bulb, and is
obviously "paired up" with the other bulb on the opposite side of the
vehicle.
I have known it to light continuously, because the two of the bulbs in my
brake lights were made by different manufactures and had differing
resistances.
You need to check that all the connections to the bulb and bulb holders are
clean.
Or perhaps replace both stop lamp bulbs.
hope this helps,
Steve.
