I purchased a 1994 s500 with 72,000 miles on it.
There were few issues with it when I got it but the seller basically was hiding a lot from me about things I could not check by myself. When I drive the car, the engine was smooth and the tranny shifted like normal. Even the brakes worked ok with no shuddering. Lots of power. The car did sit for extended period of time. This was according to the previous owner.

1. The rear sounded like the wheel bearings were gone. The noise was like a typical wheel bearing or probably the tires. This was my assessment.
When I took it to a mechanic who seemed to know what he was doing, he indicated this to me as well but now tells me that the noise originates from the differential at the rear.
2. The rear suspension was jumping too much. The mechanic replaced the accumulators and the problem seems to be fixed.
3. There is a suction pipe leaking label on the air conditioning system. I assume that it needs to be replaced? This is a typical problem I am told.
4. The central locking system (only with assist) at first did not work except for the rear drivers door. Then even that stopped. The mechanic indicated that the vacuum pump was not working. It did not make sense to me that the locks would work with the key. The mechanic pressured the hoses and indicated that they were no leaks. He claimed that there was less suction to power the assist module. I did not believe him on this one.
I played around the fuses located at the rear in the trunk to see if the fuse was the problem. When I pulled it out and put it back in, I noticed that the truck went down with the assist. All the doors also worked with the assist.
Now, I noticed that the trunk will lock if I slam it harder but only without the assist. Before, the trunk stayed slightly open because there was no assist.
5. Now comes the most frustrating part. There is a electrical problem with the car that I am unable to troubleshoot. The signals don't work properly. The right signal will work when I turn it on. When I flick the signal to the left, the right still flashes. On both positions, only the right hand signal flashes.
The headlight will come on when you start the car. However, the night lights will not come on when you turn the switch to the "ON" position. The high beams come on.
The radio was not working before. When I fixed the radio and plugged it back with the correct code, it works very well. However, I noticed that the power to the radio would kick in and out causing some sort of intermittent problem. I hear a chatter in the entire car like a constant clicking from all around in the doors. This does not happen with the radio unplugged. The power antenna is broken.
6. The Sunroof opens and closes but very sluggish. It will open half way and get stuck. Looks like it was never opened and closed and has become stiff.
7. The heater fan did not work at first. Replaced the resistor and it works now.

I am quite handy to troubleshoot electrical problems as long as I know what I am looking for with some assistance. I checked all the fuses on the front and back but unable to locate the relays that control the signal lights. It is possible that someone may have switched something around or tried to repair this problem not knowing what they were doing. The fact that I would get some of it figured out on my own, is encouraging me to complete the exercise and undo previous damage.

Would like some assistance from someone who probably knows these problems and can help me in the right direction.

Thank you kindly

 

Hey b2b,
My 94 w140 has numerous electrical "ghosts" most of which I have found to be caused by allegedly defective Delphi wiring harnesses. I say allegedly because MB won't replace them ( not that they aren't defective). In my case, I'm replacing them as I can afford them. I wish you all the best luck with yours. Just make sure you get a close look at the wires themselves by unwrapping them, and make sure they aren't brittle and crumbling like mine.
Lew