Originally Posted by bobs
Sounds like we need to check this with a volt meter! Personally, I find it hard to believe that the heaters would be on all the time. That just doesn't make sense because it would contribute to a premature failure in the heaters and cause an undue load on the electrical system.
Right. The only situation when you need to heat the mirrors is when they got fogged or when there is some ice after standing in snow. Fog appears with a quick change of temperature and humidity (tunnel, garage). Ice should be removed manually. I see no need for the system to heat permanently. In the past years I used the mirror heater only a few times. Mostly when driving into a parking garage and got to back up.