Car power seats come with varied features to create the best possible position for driver and passenger. Some even include computer memory to program specific positions for each driver and passenger. Here we will deal with simple but common power seats to test from switches, electric reversible motors and drive assemblies to wiring and steel cables. The trick when diagnosing car power seats is to focus on the mechanical or electrical problem areas: the mechanism that fails to lower and raise the seat, or the part that slides or tilts the seat forward and backwards. Keep this in mind as you troubleshoot your power seat, whether it comes with one, two or three motors. You only need very basic knowledge of electricity or the desire to learn basic troubleshooting procedures. So let’s start.
Search for one of the most common troubles in power seats: inspect the seat rails and the area under the seat with a flashlight and make sure there are no objects obstructing or preventing seat movement.
Inspect the fuse or circuit breaker if both front power seats fail to operate.
Turn on the ignition switch, but do not start the engine. Operate the power seat switch and listen for the motor running under the failed seat. If you do not hear any sound coming from the motor, lift the switch from the door panel or the side of the seat.
Check for incoming voltage at the switch using a test light. If there is no voltage, check the wiring between the switch and the fuse panel for an open or short.
Unplug the switch and test it for continuity using a multimeter. If there is no continuity, replace the switch.
Test the relay if your circuit has one between the switch and the failed motor. Operate the switch and make sure the relay is receiving voltage from the switch; also, test for outgoing voltage from the relay to the motor using a test light. Make sure the relay is properly grounded. Remove or move the seat to the side if possible for this test. If one of the voltages is not present, check that part of the wire for an open or short. If there is no outgoing voltage, test the relay for proper operation and replace it if necessary.
Check for incoming voltage at the failed motor or motors using a test light. If there is no incoming voltage, test the wire or wires for continuity between the motor and switch or relay, looking for an open or a short.
Unplug the failed motor and test it outside, connecting the motor to the car battery using two jumper wires. If the motor still does not operate, replace it.
Inspect the drive assembly-transmission, gears and tracks-and make sure the mechanism is in good condition. Make repairs as necessary.
Switches and motors are the most common trouble spots for power seats.
It is a good idea to work with the wiring diagram for your power seats on hand. Most vehicle service manuals come with wiring diagrams for the different electrical systems.
Buy a service manual at most auto parts store or consult one for free at your local public library.