Weird electrical problem on '90 300E
 

I bought a 300E two months ago, and ever since I have owned the car, the rear dome light has only worked with the switch on the dash; never with the rear doors. Last night, I opened up the rear door and the light came on to my amazement, but today, it is back to not working again. The only thing I can think of that would have to do with this is that it was raining last night and I was using the wiper...Usually the intermittent mode does not work (i think due to an old relay), but last night, for a while, the intermittant mode was working, and at the same time, so was the rear dome light with the rear doors. This is the only connection I can think of. Do these two things share the same relay, and if so, where is it so I can replace it? Sorry for the long post. Thanks guys - Mikey