A6 c7 heater blowing cold

[Gavin70248]

Advice needed, 

My A6 has a heating problem, drivers side cold and passenger side hot, I'm thinking the matrix is clogged. Any suggestions on the procedure to unclog without removing matrix .......  I've done a diagnostic and everything thing is coming up as a pass.  Any suggestions are really appreciated 

Gavin.

[Magnet]

Hello Gavin,

Heat out of the passenger side logically suggests the heater matrix is allowing hot water through it - unless of course there are two matrixes!  - which is highly doubtful. More likely to be a heater flap control issue. 
Kind regards,

Gareth. 

[Gavin70248]

Thanks, I'll have a look tonight. 

[Gavin70248]

There is plenty of air coming through the drivers footwell,  just what's coming out is cold ??

[Magnet]

So does that still lead you to think the heater matrix is blocked because one side works and one side doesn’t.? 

[Gavin70248]

That's what I'm thinking, diagnostic is saying everything is OK so my next step is to flush the system. 

[Magnet]

Sorry Gavin, I give up now. 
Kind regards,

Gareth. 

[Gavin70248]

Sorry for the late reply, been busy. The heater matrix was blocked and had to be replaced, all good now. The dealer I bought the car from repaired it for me, free of charge, which probably cost him a fortune as he had to buy matrix from Audi. He did say its something he's going to check on any audi trade-in from now on.  So if anyone is buying private please check this. 

Cheers

 

Gavin. 

[Steve Q]

Glad you got sorted 🙂

[Magnet]

Apologies Gavin, but I’m still trying to get a logical understanding on this. 
Symptoms:- 

Passenger side hot.

Driver side cold. 

You suspected a blocked heater matrix. I countered this suspicion since a blocked matrix cannot feed hot water to one side and not the other, unless there are two matrixes - each feeding one side only.

If there are two, then indeed it makes sense. Does anyone know whether this model is fitted with two independent heater matrixes, each feeding independent sides of the vehicle? 
Kind regards,

Gareth. 

[Gavin70248]

Morning Gareth, 

According to the garage the matrix had a blockage which was causing the problem. New matrix solved it. 

Gavin. 

[Entwood]

Might not be relevant at all, but a similar problem (heat one side cold the other) on a different car was also caused by a partially blocked matrix. It seems that a partial blockage allows a very low flow that provides a bit of hot water to give heat to one side, but once thats gone the "other" side only has lukewarm/cold water flow, so generates no heat at the vents. Replacing the matrix with a "freeflowing" one solves the problem as both sides get plenty of hot water. Hope that helps, although I accept it might not !!

[Magnet]

Thanks Nigel,

So if Gavin had turned the passenger side heater control down to a much lower temperature, he would have had heating on the driver side - ? 
Kind regards,

Gareth. 

[Gavin70248]

Just like to add, no matter what the heating controls were at,  the drivers side was cold due the blocked matrix. New matrix fixed problem. 

[Magnet]

So Nigel’s theory didn’t work in your case. 

[Gavin70248]

Afraid not. 

[Matrix44]

Hi everyone, i have also problem like yours, have Audi A6 4g 2013, drivers side is hot, and passenger side blowing cold air, i have done diagnostic, no error codes, i dissasembly and clean water electromagnetic valve under the windscreen and did not fix problem, you think that matrix is clogged? So one matrix is feeding both sides? 

[Stevey Y]

11 hours ago, Matrix44 said:

Hi everyone, i have also problem like yours, have Audi A6 4g 2013, drivers side is hot, and passenger side blowing cold air, i have done diagnostic, no error codes, i dissasembly and clean water electromagnetic valve under the windscreen and did not fix problem, you think that matrix is clogged? So one matrix is feeding both sides? 

Hi there is only one matrix fortunately, you could try flushing it with a jet wash as the inlet and outlet are reasonably accessible, the blockage is usually caused by the stupid silica bag in the expansion tank rupturing and dumping the crystals in the cooling system which blocks the small channels in the matrix.

Steve.

[Matrix44]

On 11/18/2024 at 11:07 AM, Stevey Y said:

Hi there is only one matrix fortunately, you could try flushing it with a jet wash as the inlet and outlet are reasonably accessible, the blockage is usually caused by the stupid silica bag in the expansion tank rupturing and dumping the crystals in the cooling system which blocks the small channels in the matrix.

Steve.

Thanks Steve i will try flush it, is it possible to change matrix from passenger side like on old audi A6 c6? 

[Stevey Y]

10 hours ago, Matrix44 said:

Thanks Steve i will try flush it, is it possible to change matrix from passenger side like on old audi A6 c6? 

Hi yes but there is a lot more to remove to get to it, try flushing it on the inlet then in reverse on the outlet, you have to give it a couple of goes but that method cleared mine.

Steve.

[Matrix44]

On 11/20/2024 at 8:16 PM, Stevey Y said:

Hi yes but there is a lot more to remove to get to it, try flushing it on the inlet then in reverse on the outlet, you have to give it a couple of goes but that method cleared mine.

Steve.

Hi steve, i flushed the heater with water for about 10min, there a lot of dirt comming out the heater, you can see on picture, so after 10min it comming clear water from heater, and connect everything and thats fix the problem, now i have hot air on passenger side also, so that fixed the problem thanks a lot. 

[Stevey Y]

16 minutes ago, Matrix44 said:

Hi steve, i flushed the heater with water for about 10min, there a lot of dirt comming out the heater, you can see on picture, so after 10min it comming clear water from heater, and connect everything and thats fix the problem, now i have hot air on passenger side also, so that fixed the problem thanks a lot. 

Hi, well done, a lot of that is accumulated rust and crud from the block, I would recommend  a complete drain down of the system and a refill with good quality antifreeze to prevent it happening in the future.

Steve.

[Steve Q]

2 hours ago, Matrix44 said:

Hi steve, i flushed the heater with water for about 10min, there a lot of dirt comming out the heater, you can see on picture, so after 10min it comming clear water from heater, and connect everything and thats fix the problem, now i have hot air on passenger side also, so that fixed the problem thanks a lot. 

Great work! 👍 

[cliffcoggin]

2 hours ago, Stevey Y said:

Hi, well done, a lot of that is accumulated rust and crud from the block, I would recommend  a complete drain down of the system and a refill with good quality antifreeze to prevent it happening in the future.

Steve.

I second that recommendation. Decent antifreeze has corrosion inhibitors to prevent that sort of corrosion; the cheap stuff does not.