Hey, the advice I got here helped me fix my first problem so I thought I would try it again.

My 1987 300E has a very strange electrical problem; with all of the fuses installed, the radio turns on and the antenna extends and retracts when the car is completely turned off. When the radio fuse is removed, the radio turns on when the car is running and a door is open. Also, the rear overhead light remains on at all times. Any ideas?

-Thanks

 

Do you have CD player built in, or cassette player?
When you insert the cassette, it supposable activates the radio.
Sometimes the switch inside gets loose and activates on its own with some vibration.
This way, or another sounds like ghost story. Keep us posted.

 

the diode of comfort circuit for power windows and seat adjustment is faulty. you got electric seat adjustment...right?
replace the diode. ensure that the comfort circuit at the correct door contact switch is connected. did you touch that door switch recently? if the connection of the two door switches are mixed up, the diode will be faulty again.

where is that diode?

it is located in a 2-pin coupling in coupler bay I of the relay holder.

where is the relay holder? (if you are planning to ask this question, let some technician do it for you).

try fix this first and we'll see about the rear lamp later. maybe they have the same ....

 

I have had a weird electrical problem with wipers/turn signal relay, another "ghost"-type situation, and resolved it by cleaning the relay pins with electrical contact cleaner. I think these older vehicles can collect dust/dirt/crap/etc which cause poor conduction at the relays, and cleaning is a simple and easy thing to try first. If it doesn't work, then maybe change the relay itself. (My relay box ('94 E420) is directly behind the fuse box under the hood.)

 

very true also.

you can see the yellowish stain on contact surfaces.