Heated Mirrors: Retrofit for Audi A6 Avant 2.5 TDI

hello everyone,
Can anyone give me some tips on retrofitting heated exterior mirrors?
The starting point is electrically adjustable mirrors, but unfortunately, they are not heated. Inside the mirror housings, there are already two black cables, but they do not carry any electricity, not even when the heated rear window is in operation. I've already figured out that they are connected in parallel. Do I just need to replace the mirror glass and run separate cables from the switch to the mirrors for the heating function, or is the process more complicated?

I am grateful for any tips.

greeting inside

Hmm, normally, this should work with the appropriate glassware. The voltage is pulsed (provided the outside temperature is below 15°C; otherwise, no heating is applied). Did you take that into account in your measurement?

Hi,
If the mirrors are electrically adjustable, they should also be heated. At least, that was the standard configuration from the factory.
It's possible that the mirror glass has been replaced at some point.
Normally, the mirror heating is activated along with the rear window heating when the outside temperature falls below a certain level; I cannot say whether the supply voltage is pulsed or not.
However, the heating effect diminishes over the years; it seems that the resistance of the heater increases, and consequently, only a small amount of current flows.
Heated mirror glass is significantly (!) cheaper to buy from accessory shops than from dealerships.

Regards,

Olli.