Originally Posted by Jeburnett

I read about the 59 degree setting from some Goggle searches I had done a few months back. It wasn't until we had some real temperature drops that I had the opportunity to see the heaters turn on. It was in the 50's somewhat below 59 so it seemed consistent with the reference I had read.

I've spoken with the service guys at the dealership and they didn't even know about the limit and couldn't answer if it was override-able.

Originally Posted by Jeburnett

I just did an experiment. The outside temperature had fallen to 68-69 degrees, so I got in the car and using one of those infrared "laser" thermometers, I read the mirror temperature to be 68 degrees. When I switched the **** to mirror-heat, the instrument dash reported the mirror heat came on and using the thermometer, I could read an immediate temperature rise. After a few minutes, it seemed to stabilize around 79 degrees, or 10 degrees above ambient. The heat stayed on and so did the display UNTIL I rotated the **** to turn off the heat, which naturally turned it off. When I turned heat back on, the mirror did NOT heat up and the instrument display confirmed as such. I waited for the mirror temperature to fall back below 69 and when it did, the mirror heat did not come back on. I turned off the Q7 and restarted and this time when I turned the mirror heat on, it came on. Briefly turning it off and back on caused both actions to occur.

So, this pretty much confirms 69 degrees as the trigger temperature AND it confirms that the thermistor the car is using for that purpose is in the mirror itself, rather than the vehicle thermistor.

Not sure what it says about the vehicle cycling experience but that may have just coincided with some timeout period (i.e. max number of minutes the heat is on).

Interesting observations...