[QUOTE=a_2000_se;4579342]Of the many type of sensors it's probably a thermistor - fairly inexpensive - resistance changes with temperature. And since they have changed the mirror assembly already then it points to a problem with a connector/contact/resistance that is changing slightly with temp or vibration. Mirrors aren't heated on a 2012/focus?[/QUOTE
The mirrors are not heated on my car.
The connectors is something I heard one of the Ford mechanics mention but they did not look any further since it was within the + or - 3 degrees at the time which met factory specs.
I would not mind testing the connectors myself. I am guessing there is one at the mirror assembly and one more under the dash somewhere? I would guess I am just looking for loose connections and checking the resistance with a multi meter?