I have a 2009 S40 with power driver's side seat. The passenger side seat is manual. The driver's power seat suddenly stopped moving, it will not move in any direction, nor will the back recline. I checked fuse 85 and it had a little bit of brown spots on the pins, but showed continuity when I tested it,but I replaced it anyway. The seat still didn't work, however after I wiggled the seat around,it started working again. Then for a couple days,it worked intermittently, now stopped working again entirely.

On a possibly related note, there is a water leak in the interior of the car and often the drivers side rear floorboard is soaking wet. Is it likely that water has damaged anything under the seat causing a bad connection?

 

Problem a: My experience with the seat controls: There is a limit circuit in the seat switch that turns off the active drive motor is the voltage drops too much. With the switch removed, each of the motors worked just fine when I jumpered it directly to 12V. The voltage drop is measured between the primary supply line and a reference voltage line. (Page 136 of the wiring diagrams, Module 3/26, the "Stop logic" section) In my car, I think there is either a fault in the reference line or a voltage drop in the supply line (30P: RD-BU). I jumpered the "Stop logic" relay, and have had no problems. When I get to the end of travel, I let go of the switch.

Problem b: I would a) pull those seats and all the carpet and dry them out. There is no way they will dry in the car, and EVERY electrical control in the car is run under that carpet. The insulation is pretty good, but there's a limit. b) I would look at all the "my moonroof is leaking" threads and discover the source of the water. c) Personally, I added a water alarm under the carpet under the "A" pillar to get an early warning of a repeat leak.

Mark

 

I am having the same problem and would like to try your solution.

 

Bonne chance! It worked for me for about 2 years, until rust on the bare steel frame brought the works to a standstill. Sigh. Junk seat frames are apparently on eBay for $150 or so. I may try that, or just live with a frozen fore-aft track (and various SRS warnings).

As to how to put the jumper in, I gave the relevant wiring diagram, which can be discovered on the web. The actual parts are on the control board behind the seat controls. It can be removed for inspection (or more) without removing the seat. The power for the motors comes in through pin 5, and excess current draw is sensed and cut off by the "stop logic" relay. If you jump the relay and connect pin 5 to the supply bus for the motors, everything works still, except that you need to THINK and stop "hitting the button" when you reach the end of travel. If you don't, things can melt.