On my 1984 190E, it is simple - there are a couple of tabs at the bottom of the back seat (where your heels would be if you were sittng), you have to look, the seat will pull right out!
It's probably the switch.
The motors are underneath the seats
Photos of tabs to remove
Jack hammer
I have a 1987 Mercedes that has no trunk key. Do I remove the back seat to get in?
Its on the door panel next to the door handle. at least that's where it is on my 1992 190e 2.3
You have to remove the entire door panel. Some models are screwed on and some models just snap on. For the very best advise, take it to you closes Mercedes-Benz dealer. Good luck!
Remove seat!
find the "hole" in the back of the seat. ... wait a sec.. read your manual.
Move the seats all the way back, unbolt the two bolts holding the front of the frame to the floor. Move the seat all the way forward, and remove the two bolts in the back. Tilt the seat back, and unclip the wires underneath the seat.
Move the seat all the way back. Remove the two bolts in front of the base of the seat. Move the seat all the way forward. Remove both bolts at the base of the rear. Wiggle the seat until it comes loose and look for wires underneath that may go to the seat motor and seat warmers.
there are two bolts in the back of the seat. remove them and then slide the seat back about an inch and remove