I have a 2014 A3 S line that I've recently purchased and noticed the other week that the heating is not working. I get a slight bit of warmth from the passenger side vents but that's it. All the vents appear to working fine when I change the controls, and I can hear a difference in the air flow when i move between hot and cold. I had another job done today and my mechanic has plugged in and there is no faults logged with regards to heating. 

Looking into it I can see there is a common fault with the matrix core blocking up. Both the inlet and outlet pipes from the matrix are both getting hot when the engine is upto temp. The temp on the car gets up to 90 degrees and stays there regardless of how far I travel. There appears to be no leaks in the cooling system either.

I've convinced myself that the core needs replacing but having hot pipes on the inlet and outlet has me doubting that uneducated guess! I'm thinking for the sake of £60 I'll replace the core (with assistance!) and see what the outcome is. 

Does anyone have an ideas on other potential things to check? My father in law is a retired mechanic and he wants to check the blending flaps first which we will do, but I'm guessing any faults with those motors would show up on the diagnostics?

Many thanks!

Just had to top up around 300ml of water in the header tank as I had a low coolant level on the dash. I checked under the car and there appears to be no sign of coolant on the floor.

Any help greatly appreciated 😭

Could be head gasket. Any smoke from exhaust? 

Or heater matrix. 

I'd recommend a diagnostic check to see if any fault codes flag up 

Thanks Steve. No faults are showing on a diagnostic check. There doesn't appear to be any smoke and the oil looks fine. 

I've ordered a new matrix core so hopefully that does the job!

Fingers crossed it's the matrix 🤞

So changed the matrix core today and heating is restored just in time for summer 🤣. Was a bit of a fiddly job, about 2 hours in total. Strangely enough, there was no sign of the silica bag in the coolant tank. Possibly removed by a previous owner? Who knows. 

I did notice a week or so ago the radiator seems to kick in a bit even though the engine temp sits at 90 degrees. It done it again today after the matrix core had been replaced. Possibly another issue that needs looking at.