I have a 2007 Navigator with 125,000 miles. The passenger side mirror will not retract automatically, the driver side works fine. The passenger side mirror glass adjusts fine, so it is getting power, it just won't retract. I have followed the reset procedure several times, but it still won't work. There is no clicking at all. Are there gears that can be replaced?

 

I don't think anybody sells just the gears for power mirrors. It could be the motor that retracts while the motor to move the mirrors works ok.
It does sound like an electrical problem. Just my guess.
Richard