Supplementary Heater

[Cantata]

I have an A6 Avant SE, 3.0Tdi, lovely car, coming up to 10 years old, all good and only 73k miles on it.
After owning it for 8 years and always suffering lack of heat for the first 20 minutes or so on winter mornings, my wife discovered something the other day. On one such cold morning, she pressed one of the air direction buttons at the bottom of the heater panel while the engine was still stone cold, and loads of hot air started coming out!
Presumably an electric heater? Or heated by the exhaust?
Looked in the instruction manual, it mentions a ‘Supplementary Heater’ without explaining what it is. It says that on a diesel car, and if the heating is set on Auto, this supplementary heater is automatically used if needed. But on my car, that doesn’t appear to happen, it’s only if you use the direction buttons. So, can anyone explain about this please?

 

[NHN]

There's 2 systems, 1 is aux heater specifically for diesels as they dont heat up that quick as opposed to petrol, its fitted behind the matrix usually, 2nd is a specific heater fitted in the engine bay that's a spec'd feature, not usually fitted in warmer climates including uk, but Nordic afaik its a standard feature, runs of the fuel system & allows preheating of the car via your remote, signalled to the sharkfin usually, its hardly ever spec'd here.

 

[Cantata]

Thanks NHN. So what I have is presumably what you describe as the 'aux heater' behind the normal matrix. Odd though that it doesn't make itself known without using the air direction buttons. Still, nice to find an extra useful feature after 8 years of ownership!

 

[NHN]

Afaik it should work regardless of the air direction selected, as its usually bolted to the matrix so it should work, maybe its a stuck flap that selecting the direction unhooks.

 

[Cantata]

Sounds possible doesn't it. Not really worth investigating on its own, though. Thanks for the thought.

 

[NHN]

The fact as soon as you move flaps it works, tells me it could be a motor, cog or flap issue.

So if you set it back to non directional after hot air starts to come out, when directional, does it stop or does the hot air continue from then on?

 

[Cantata]

I'll try that next time out. Up to now I've left the directional set until the thermostat opens, then go back to Auto.