Manually Resetting the Damper Motor

[drvolvo]

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 foot well, you can access the damper motor for removal. You also have to remove the wires that unclip easily from the back of the damper motor.

There are three screws holding the damper motor in. You can see the three screw holes from this photo. (Ignore the hole on the far left of the unit) One of the screws is a real pain to reach, but it is doable.

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.

I recalled prior contributions from others who sent me documents about the damper motor location. In particular a PDF mentioned calibrating the damper motor. I will post all PDFs here

S40-2001-DamperMotorSelfAdjustment-1.pdf

(127.31 KiB) Downloaded 7054 times

S40-2001-TemperatureDamperMotorAdjustment.pdf

(40.41 KiB) Downloaded 5338 times

S40TempDamperMotor2001.pdf

(44.43 KiB) Downloaded 4451 times

Based on this information I had to move the damper motor arm to a position where the arm was as far away as possible from the actual unit. The picture I posted above shows the arm at the most inward position. So what I did was use the 9 volt to move the arm out. Then make sure the temperature dial setting is at zero (coldest position) before you turn on the car. (See the second pdf attachment)

With the arm in the furthest outward position, I attached the metal arm that connects to the actual damper, and then started the car. Lo and behold, the damper arm moved as described in the self adjustment pdf and I am proud to say my damper motor works!!!

Victory is Mine (and yours too if you have this same problem).

This procedure is also important if you were to purchase a new damper motor. To begin, the damper arm must be fully extended. Now there might be a more sophisticated way of moving the arm aside from using a 9 volt, but at least my procedure avoids the stealership.

[matthew1]

Outstanding, good work Dr. Pinned in the Repair Database.