You probably have a broken damper arm or motor. How do you do a VOLVO DAMPER MOTOR REPAIR?
Dr. Volvo writes:
Can I do a Volvo damper motor repair? My damper motor stopped responding to changes in the temperature dial, leaving me with a car that was either 100% on full heat or 100% on cold. Eventually, I disconnected the damper motor arm so that I could just change the damper myself manually. This was a pain, though, since I’d have to remove the radio to access the damper arm.
Here is a picture of the damper motor with the arm removed. This is visible once you remove the radio.
If you also remove the side panel on the passenger side footwell, you can access the damper motor for removal. You also have to remove the wires, which un-clip easily from the back of the damper motor.
How did we get here?
On another thread discussing a faulty damper motor, someone commented something to the effect that ‘if it is already broken, what’s the harm in taking it apart to see why’. So I was motivated by this sentiment and I removed the damper motor and decided to remove the back cover to get at the parts inside. There are clips all along the outside of the damper motor. If you can wiggle the clips (and use toothpicks or something else to hold the clips apart as you work around the unit) you can get the cover off the unit. Unfortunately I failed to snap a picture of the damper motor with the cover off. The mechanisms looked fine and everything seemed to move freely. The motor at the end of the unit has two contact points. I am not overly technical or electrical (ok, not at all), but I figured, what the heck, why not try to stick a 9 volt battery to the end of the motor to see what happens? And lo and behold, the motor starts and moves the unit’s arm to one extreme. If I switched the 9 volt battery prongs 180 degrees , the unit moved in the opposite direction. So I knew the motor itself worked.