heated mirrors

On my Volvo, I have to hold the button down for several seconds for it to stay on. When I push and release it so it's flashing, the mirror only heats for a short time, such as to clear it when it fogs up, then it shuts down again.

 

Ugh,lucky you to even need it! So hot down South!!!

 

We have been a little warm down here this year. I haven't turned on a mirror heater since Feb.

 

mirror heat MOSFET is in button assembly. Usually goes bad if you keep door open when it is raining

 

A MOSFET, in layman terms, is just a transistor (electrical part) on the control switch.

 

Sounds exactly like what I had to deal with. A new switch didn’t fix the problem. It did turn out to be a short to ground on the power side of the circuit. But, I would first check the wires that go into the mirror. Make sure you remove the mirror mount and check the condition of the wires under that as well. This is the most common issue. What I found was that under the passenger side kick panel, the wires were pinched by a bolt, causing the short. You may want to do a few checks before diving into the dash. With both your mirrors unplugged, check your power side circuit for resistance to ground to ensure it’s not shorted. Your voltmeter should read an open circuit. I read 25M ohms and that was enough to cause the problems.

Hope this helps anyone else seeking a solution.