89 525i - Electrical Prob.-Windows,Wiper,Sunroof

Someone please help. There are times when i turn on my 525i and the wipers, sunroof, and pwr windows work. Sometimes they don't. The funny thing is that they are all link together somehow and I cannot figure it out. I know its not a fuse and I switch out the 2 black boxes from underneath the back seat on the driver side. Can someone tell me where else to look as I cannot afford to have it check by a Certified BMW mechanic.

Thank you so much.

i work for a bmw specialist in aus, it sounds like you may have a short in your body control module which could cause everything to be powered up at once, im not sure how much different yours is to the australian ones but under the passengers side dash you should find all the bcm's and check all the wires and also where the wires exit through into the engine bay make sure that they havnt split there

Your vehicle is an E34 5 series. Remove the rear seat and follow the smaller diameter possitive cable to a black plastic box approx 3" wide. Open the box and you will see a metal fused link shaped like a spanner and held in with two 8mm bolts. Remove the two bolts and fused link (normally this link is broken and the break can only be seen by removal.) if the link is not under the rear seat, some E34s have the link fitted on the offside front suspension turret under the bonnet (but the majority are fitted under the rear seat) this fuse controls circuits from the relay module which in turn work the sunroof, wipers and electric windows. If this fuse is OK, the fault will be with the relay module (under the rear seat and shaped like a VHS video) No dealer resets will be necessary.