I recently bought a 2002 Volvo S40 that had non-functional interior lights and sunroof controls. The person I bought the car from assured me that all I needed to do was replace that assembly. However, when I bought a used one from ebay and tried installing it, I discovered that there was no power getting to the assembly. My brother (who is a mechanic but doesn't work on foreign cars) traced the problem to an unplugged connector from the wiring leading from the assembly, across the roof and down the driver's side strut in between the windshield and the door, down into the engine compartment. (The unplugged connector itself was near the bottom of the strut.) When we plugged the connector back in, the interior lights and sunroof control started working. However...

The next morning, I started the car and noticed that the radio antenna did not go up. I also noticed that the car's clock had not changed its time from when I'd shut it off the previous evening. When I started it again later on that day, the radio asked for the reset code.

I'm guessing that there's some kind of short in the system, and that's why the previous owner had the connector unplugged (and naturally didn't explain that to me). How would I track this problem down? I'm not a car expert and although I could easily buy a Chilton's or Haynes manual for the car, I wouldn't know how to use it to trace the problem.

Suggestions?

Damon