I've been having some intermittent air mix motor problems for the last year or so. Pretty randomly, I'm unable to adjust the temperature. Usually you can hear the motor running but once in a while it does not move. Initially I did try and clean the contacts and I thought it was better but unfortunately it came back.

I disconnected the motor and let it hang and every once in a while I turned the dial and watched it. Last week I finally caught it in the act and I saw/hear the motor struggle and turn very roughly. Almost jumping and not smooth. Really weird...

In any case I opened it up again and took a closer look. It looked like the teeth on the plastic gear were worn. Now it only uses about 1/4 of the gears on the wheel and lucky for me the contacts on it are symmetrical. So what I did was rotated it 180 degrees and reinstalled with fresh grease. This way the plastic gear is now contacting the motor with basically new teeth. Pictures below will clarify better

Should be good for another 30 years.

This picture show the arm in the cold position



These pictures shows the gear and contacts. It's a pretty straight forward mod. Just be careful not to break the casing when first removing the arm.

The dark teeth on the gear are the original contact points.

 

hard to tell from the photos, but they don't look to be that worn. It must be close tolerances...anyway, good fix. This is going to be the only way to maintain this stuff on these cars over the coming years.