Audi Repair Questions? Ask a Mechanic for Answers ASAP
Very first thing to do is ensure the coolant level is up to the mark and if low top it up with the correct antifreeze or pre-mixed coolant as stated in the owners manual
I'd then check that the engine is getting up to temperature, - are the radiator hoses hot and the temp gauge reaching the middle position?
If this is OK have a feel of the two coolant pipes that pass into the car through the engine bay bulkhead, both should be warm with a warm engine. If they're not then its likely the heater matrix is blocked and you should do a reverse flush on the cooling system to try and clean it out. This is done by removing the top hose from the radiator and placing a garden hose into the engine water outlet, and then run the hose until you get clean water coming out of the radiator.
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