Audi A3 8pa sportback rear window/mirrors heater not working

[vdk]

Hello I have an Audi A3 8pa sportback 2.0tdi 140hp. I have the following problem, it's usually when the temperature outside is low. Whenever I press the button that starts the rear window/mirror heaters it starts for 1-2 seconds and stops and if I press it again, the same thing, as I mentioned above the problem occurs when the outside temperature Is low(below maybe 4-5 degrees Celsius). Could someone please help? Thanks!

 

[Sibmets]

You should scan for fault codes. On my B6 I had the same symptoms and the fault code said that the climate control unit is faulty - replaced it and voila - it started to work.

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[vdk]

I've had this problem for a couple of years now and i've scanned for fault codes and nothing has come up .

 

[Sibmets]

Did You got it scanned with VCDS/obd11 or with generic scanner?
If You hold the defrost button pressed, does your rear windshield gets warm?

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[vdk]

I scanned it on obd and the service guy also scanned it and nothing came up.
I've tried holding the button but it doesn't do anything.

 

[ch1z64]

Might be worth finding out what wire from Ac plug does the back window heater and check it to see its not broken corroded , maybe even loss ie not seated in plug correctly

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[vdk]

I only have this problem when the outside temperature is below 5 degrees Celsius. The other time it works without a problem. I read somewhere the when the temperature falls below 5 degrees Celsius the mirror and read window heaters are automatically turned ON. Maybe that part is the problem it doesn't let me turn it ON since it's supposed to be working anyway, but it's bugged or something.

 

[Sibmets]

They definitely doesn't turn on automatically on my wives A3 8P. And mirror heating turns on only by using the dedicated mirror heating switch on the driver door - regardless of rear window heating button position.
In warm weather they don't work, because they're supposed to switch of when they reach something around +20°C.

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[vdk]

Yes, you are correct, i was talking about only about the rear window heater(sorry i mentioned the mirror heaters as well).

 

[vdk]

i've checked everything and my left mirror heater had to be cleaned a bit and now works fine, but i still have the issue with the rear window defogger when outside temperature is cold, checked everything related to it and there wre no issues(fuse, wires, plugs...). Does anyone know what could be the cause, i know that in the winter season when the temperature is low, the battery cosumes more to start the car and that may cause issues, but i doubt that is the problem since i've never had issues starting the car and the battery is fairly new and i've recently check it as well.