Clicking Noise, Power Seats, 1985 300SD
 

On driver's side seat, all power functions work fine except for the motors that raise/lower the front and back of the seats. I've tested the switch and it is good. All I get is a click from under the seat (control relay) when I try to raise or lower the front, and the same on the back. Is this a motor issue or a relay issue? Can I bypass the relay if I don't care about the memory functions?

if the relay clicks, i'd think the motor was bad, but check to make sure the wiring isn't damaged or disconnected.

Took off the four bolts that hold seat in place to be able to tilt it back and study the wiring and motors. There is a control box with a bunch of relays and separate connectors that feed all the motors. I found that if I rock the connectors back and forth I can get that seat tilt motor to operate just fine. But looking at the connectors, they look clean. So my theory is that the internal connections in the relay box might not be in very good condition. I cannot seem to get it to work without the wiggling. If I stop the wiggling, it stops working. Does this seem like I control box problem? Has anyone ever taken that box apart to clean or repair the inside?

The wiring diagram says its a solid state controller, and the connections from the switches indicate that the switches apply a control signal to the box and the box then applies power and ground to the motor. The controller could probably be removed and disassembled, but it would be easier to check the connector to the motor first. Disassemble the connector and check the two large sockets. Make sure the wiring is solid. You might try squeezing the sockets down a bit to make a better connection with the pins on the controller.

It looks like there's a squarish cover on the controller. Is that where the relays live? Are they removeable? If they're all alike, try finding the one that controls your circuit and swap it with another.

I have found that almost all the connectors or wiring at the connectors is suspect. Now two of the other motors are intermittent and require wiggling. Now that I think about it, the seat controls have kind of been unreliable, so I think there are few connectors with this issue. Maybe the round reciever tubes are worn and are not fitting snugly.

by receiver tubes, I assume you mean the female sockets inside the connectors. Yes, this is what I meant previously when I said to squeeze them down to make a better connection with the pins on the controller. If the wiring to the sockets is good this wouldn't hurt. Take care not to over-correct, though. You don't want to deform the sockets or you may have a problem with getting the plug back on. You'll need to disassemble the connector to do it properly. Don't even attempt to fix it with the socket still inside the connector.

Yeah, that all makes sense. I will give that a shot. I think the wiring is good, because when I wiggle the wires i get no change. But as soon as I wiggle that connector, motor comes to life.

loose female pins are common on MB's. fixed more than a few problems by tightening up the pins. also if waters ever been in the car, corrosion can be a problem.

loose females are always a problem whether you have them or you don't... :thumbsup: