Troubleshooting Power Door Locks
Tools/ Supplies needed: 12 volt test light, Phillips screwdriver, flat blade screwdriver, 10mm wrench, and spray lube (like WD40).
Troubleshooting power door locks on your 200 or 700 series Volvo:
If only one or two doors are not functioning properly, you can be pretty sure that the problem is within those doors. Remove the door panels and check for 12 volts to the motors while the drivers door button is held in the lock position and then in the unlock position. 12 volts is present to the system only when the drivers lock button or lock cylinder is held with light pressure in the lock or unlock position. Beneath the drivers door lock button, inside the door is a pressure sensitive switch that sends the 12 volt signal to the relays, and reverses polarity based on it’s position. There are 2 wires connected to each motor (no motor in the drivers door). Since the polarity of these wires is switched to open or close the lock, it is best to pierce each wire and attach the ground clip of your test light to one wire, and the probe of the test light to the other. It is easier to test across the 2 terminals where the harness unplugs inside each door. If you get 12 volts in the lock and unlock positions, proceed to the motor. If you don’t get 12 volts, most likely one or both of the wires are broken in the door hinge area. Pull the wire harness further into the door to inspect for breaks, you may have to disconnect the rubber boot from the door to access wires. Repair any breaks with solder or crimp connector.
If all door locks have stopped functioning, check the fuse (#8 in 200 series, also runs the clock). If the fuse is OK, you’ve probably got a break in the wiring harness in the drivers door. Check for breaks in the wires at the pressure activated switch located at the base of the drivers door lock mechanism and where the harness flexes in the hinge area. If after repairing the wires you still have problems getting voltage to the motors, check the relays located behind the fresh air vents in the center console (200 series). If you’ve got voltage to the motors and things still aren’t working, proceed to the motor repair process next.
If you’ve determined that you have power to the motor and things still aren’t working, it’s likely that the motor has corroded internally and just needs to be cleaned. Some people have success taking motors apart and getting them to operate again. You’ll have to be the judge of your ability, and the value of your time.
Unclip the motor from the door lock mechanism, remove the two 10mm mounting nuts and remove the motor from the door. Use a small flat blade screwdriver to remove the 3 screws holding the two halves of the plastic motor housing together. Carefully pull the rubber accordion boot off the top and you should be able to separate the housings now. Inside you’ll find a small electric motor and some wire connections. There is also a small metallic disc about the size of a dime, this is usually where the corrosion occurs. Pry the disc out and clean it with sandpaper or a small wire brush. Re-assemble the motor and test it before installing it back into the door. If it still doesn’t function, it’s probably time to replace the motor.