I will begin by saying that Volvo makes an awesome car.
I recently started having issues with my ECC unit. The dreaded flashing lights. So I pulled codes, and found lots of issues, the temp fan, the blower motor, damper motor and others. I thought that the ECC control unit had given up the ghost. After looking into it, I found the temp sensor was working correctly, and the blower motor was woking properly also. Upon looking into the damper motor, I found that it was not working.
So, like any good do it yourselfer, I took the damper motor apart. I figured if it's broken, I can't break it anymore. Upon opening the housing, I found the circuit board covered in white grease. I cleaned some of it off before this pic:
The black half circles were covered in grease also. I cleaned it off, and plugged it back in. all the codes went away, and the motor operated normally.
These contacts touch the black half circles:
The grease is from the gears in the reduction system, and must have gotten on the contacts over the years.
Put everything back together, and all is well.
So, If you get the dreaded flashing lights, this is one more place to check before replacing parts.