Intermittent rear brake light issue

[sasquatch]

Most likely the problem is the conact area where the buld fits has been "burned" away due to arcing. BMW uses a poorly designed bulb "busing" system in which the bulbs can move or otherwise vibrate within the holder. It causes the contact points to become separated and they'll arc when a voltage is applied. Over time it will literally eat away the metal. Very common issue which is easily fixed.

Remove the taillight assemblies. Take out the bulbs. Take a close look at the round metal contacts and see if you can find any areas where the metal busing looks like it was melted or pitted. Clean the area and use some good quality solder to fill in the holes/pits. Sand, grind, or file smooth and flat with the metal. Reinsert the bulb and reinstall the tailight. Problem solved.

[TwinTurboGTR]

Originally Posted by sasquatch

Remove the taillight assemblies. Take out the bulbs. Take a close look at the round metal contacts and see if you can find any areas where the metal busing looks like it was melted or pitted. Clean the area and use some good quality solder to fill in the holes/pits. Sand, grind, or file smooth and flat with the metal. Reinsert the bulb and reinstall the tailight. Problem solved.

Yup, I concur. Same thing happened to my X, did that and all has been well for over 2 years.

[bakersx5]

I fought and fought. bought new bulbs etc. i finally pulled out the tail light assembly and there it was, a small hole. i took some solder and my soldering iron and patched it right up. ground it down with my dremel tool and no trouble since. what, other than a bmw, would have this kind of crap go wrong???