That is a very touchy because it could be the motor, could be the relay, and could be the multi-function switch. Most likely it is not the multi-function switch if all of the other functions are working, like the turn signals, the headlights, and the high beams. If all those are workin correctly, then it is not the switch.
Most likely it is the motor, but I replaced mine along with the multi-function switch, to find out that the relay for the system was shot. Thank god I had a spare car at the time that had a brandy new motor in it to swap that did not cost me any money. I would guess it is the motor.
Hope that helps....