Activate auxiliary heater?

Hi.

"For some time now, TDIs (and likely other engines) have no longer been 'heated' using glow plugs in the coolant, but directly via 'glow wires' in the airflow of the heating system."

How can I activate them?

Because:
If I simply leave the Climatronic (CT) running, it doesn't overheat, even when the outside temperature is below freezing and the desired indoor temperature is 20 degrees Celsius.
The "Defrost" program activates the heater, and even an immediate switch to Auto/Eco mode will leave it running.

Is "Auto-defrost-Auto" the "official" and only variant?

Can I turn this feature off again?

Okay, here's the translation:

Thank you.
m;

It should work on Audi vehicles at least when the outside temperature is below 6°C, econ mode is turned off, and the generator load is not too high, I think less than 60%, but I need to double-check that.
I'm not sure when mine actually starts heating up either. Most of the time, the auxiliary heater is already running, and in the early morning, I don't have the time or inclination to check it using VAG-Com.