Dec
Senior Member
All this depends on what type of set up you have on your car, I dare say the more recent cars have a more complex set up compared to older cars.
On mine, if the temperature of the mirror glass is below 15c while the ignition is switched on, a thermostat switch (as in picture) on the mirror back will switch the mirror heater element on and heat the glass until the 15c temperature is passed, it then switches off until the temperature of the glass drops below 15c, this cycle repeats itself every few minutes, depending on the temperature of the mirror glass.
There is always 12v going to the heater element in the mirror, it is the thermostatic switch that switches the heater element on and off.
Dec
On mine, if the temperature of the mirror glass is below 15c while the ignition is switched on, a thermostat switch (as in picture) on the mirror back will switch the mirror heater element on and heat the glass until the 15c temperature is passed, it then switches off until the temperature of the glass drops below 15c, this cycle repeats itself every few minutes, depending on the temperature of the mirror glass.
There is always 12v going to the heater element in the mirror, it is the thermostatic switch that switches the heater element on and off.
Dec