Fast Idle 2015 Jetta TDI

I have noticed when below a certain outside tempature the car goes into a fast idle when the heater is turned on. This is good as I would guess is to keep the engine and coolant at a required tempature. With the heater turned off it goes back to normal idle of about 800 rpm. The fast is about 976 rpm. I would assume others have noticed this and even posted it out here.

The auxiliary heater is 80amps and it does activate in the conditions you describe... I believe the high idle is to help reduce stress on the alternator. Of course, this is anecdotal. I will say that I can watch the avg mpg readout drop fast and only during the preheat phase.

I noticed it only does it when I have the inside temp synchronize for high temperature. If one set lower it doesn't do it so it seems. Nice future to keep even thing warm. I have a comfort line tdi.

Yeah, there is a "switch" that is activated only when the temperature dial is set to the hottest temperature. If you want to improve winter MPGs, dial the temperature dial back 1 click and that auxiliary electric heater won't activate. You can actually feel it engage/disengage the max switch.