I have had the car for about 3 months now and just recently the heater for the passenger side has stopped working. The driver's side seems to work OK, but not the passenger side. It is an 850 R wagon with the dual climate controls.

Any suggestions of things to do or look for before I take it to the dealer?

I'm sorry if I mislead you. I meant to say the Heater as in AC/Heater as in climate controls. The seat heaters are working fine.

Like the other poster mentioned, if the switch doesn't light up at all then it's probably the switch itself or the connection to that switch that has gone bad. You might also want to check the 2 wires going into the thermostat from the bottom of the seat cushion. Raise the seat as high as possible, tilt it forward and get a good look from underneath in the back seat area. There should be 2 wires that snake up into the bottom of the seat, they go into a hole and crammed in that hole is the thermostat. Check and see if these wires are still making good contact with the T-stat. Make sure the keys are not in the ignition before sticking your fingers into that hole to yank the T-stat out. If you have big hands, it may be a bit frustrating because the hole isn't that big and the T-stat may be crammed up deep.

I've got the same problem in the driver's seat. I think it's the switch because the other seat heater works (same fuse) and the switch doesn't light up anymore.

Does it work when someone is sitting in it? I believe there is a sensor in there that prevents the heater from being on if no one is sitting in the seat.