1990 Mercedes-Benz 300SL Power Seat Motor Replacement Cost

Power seat components are intended to last the lifetime of a vehicle and have no regular replacement interval. A power seat motor may wear out over time. Damage can occur to wiring or a control module mounted under the seat, especially if water is allowed to pool on the floor, such as may occur in a flood.

To check for a bad power seat motor, a technician will first make sure that a fuse has not blown. A blown fuse can be either the cause of an inoperative power seat or a symptom. It is unlikely that all of the seat motors will stop working at the same time. If the seat will not move along one axis when a switch is pressed, but works in all other directions, the technician will check for power to the switch and to the relay (more common causes of an inoperative seat function) before checking the seat motor itself. If voltage is present at the switch and at the relay, the technician will test the motor to make sure it is receiving voltage. If it has power but will not operate, the motor is likely to be defective. In some cases, the problem might originate in the seat control module or in the Body Control Module. In these cases, the technician will look for a diagnostic trouble code (a fault code) that can be read with a scan tool.

If a power seat motor is the cause of a malfunctioning seat, a technician will move the seat to expose and remove the nuts or bolts that hold the seat in place. This can be difficult if the seat malfunction prevents the seat from moving forward and backward, preventing access to the fasteners. With the seat detached from the floor, the technician will disconnect the battery, tip the seat up to access the power seat electrical connections, and unplug the wire connections. Once the seat is completely disconnected it is carefully removed from the vehicle. Depending on the location of the faulty seat motor, the seat may need to be disassembled (seat back and base separated and seat cover removed) in order to replace the motor. With the new motor in place, the technician will apply power to the circuit and test the new motor before reinstalling the seat in the vehicle.

Because the front seats are an integral component of vehicle safety, RepairPal recommends that any disassembly of the power seat be left to a professional technician.

Some vehicles incorporate Supplemental Restraint System (SRS) features into the seat, such as seat-mounted airbags and/or seatbelt pretensioners. Care is needed to avoid damage to the wires for the SRS and other components located in the seats. The SRS may need to be reset with a special scan tool after the seat is disconnected.

If replacement of a power seat motor requires that the seat be disassembled for access to the motor, the job should be left to a qualified repair professional. The integrity of the seat is essential to occupant safety in the case of a rear end crash.