HK in AK

I have a 2002 C240 that I purchased new, and it's been a great car. The driver's seat has issues: the power controls for the headrest, up/down seat adjustment, and seat back do not work. When I push the controls that radio stops playing, and there is an obvious power drain. When not pushing the controls, there is no short in the seat control wiring. The heated seat option works great, only problem is with the driver's seat, passenger seat works great!

Appreciate the help, and I hope my detail of the problem was sufficient.

jogger

did you check for fuses?

Moviela

Can you disconnect the seat module and connect a temp power supply to the motors to see if they run? It could be a shorted motor or bad wiring between the module and motor. Sometimes allowing objects to roll about on the floor pushes the wiring to a point where it might chafe, or simply moving the seat all the time might cause a wiring harness short.

The switch itself does not drive the motor. The switch is a low current signal to alert the CANbus that the motor needs to move. The seat module does the heavy lifting when the signal is received from the switches. It is possible the high current drivers in the seat module are toast.

samaritrey

I would also make sure the wires are plugged in all the way.
You may also have a bad seat control modular or heck a bad switch on the door panel.
Sounds like you have some from detective work to do this week

HK in AK

thank you for the help. I will do some digging and work on resolving the problem. Otherwise the car has been great for 10 years.

MW_ATL

Good luck, these can be very difficult to figure out. I had an issue with our SLK where if you hit the turn-signal, the A/C went out. But after it went out, if you honked the horn and then hit the A/C button again, it came back on. (Nope, wouldn't come back on without the honk). If that isn't about the weirdest combination!

Yes, it would correct itself if you turned the ignition off and back on, but since it started doing this in Tampa, and I live in Atlanta, that wasn't the answer for the drive home in summer.

End result - found by the dealer - a bad circuit board in the A/C control panel. That was an interesting one to find, and I honestly don't think I could have ever found it on my own without just throwing parts at it.

One other - your car - related thought. I believe there is a CANbus relay somewhere in there that is supposed to do things like turn power on for the seats after you open the door and such. If it is bad, since I believe the radio is also on the CANbus, it could be causing really weird issues. Unfortunately, I don't have power seats on my C, so I can't give you much more help there. (Also has the CANbus relay give problems on the SLK, but was just random no power to the seats).

RPB