I've just got the same problem with mine so will try the tip for repairing it, thanks.
I have just put in a new bulb (haven't done repairs yet) and reverse light didn't come on. Do you think this a) because its already wet, or b) cos the water has shorted / blown the bulb holder or other part?
Thanks for any advice.
Resurecting this old thread again - sorry if that's bad form - to see if anyone has come up with a permanent solution to this problem.
My reverse light is also filling up with water. The rubber washer around the bulb holder is in good condition, and I tried wrapping it with PTFE tape last time as well, so I don't think that seal is the problem.
I think steam from the exhaust might be getting in through the vent pipe or condensing on the wire and running through the tiny gaps in the bulb holder around the contacts. Beacuse the fog light on the other side, away from the exhaust, is bone dry.
Any suggestions would be much appreciated.