3.0 tdi Heater Blowing Cold - URGENT HELP!

[Mazi]

I have recently purchased a 2012 A6 Avant 3.0 TDI with a DPF fault which didnt really scare me as the car was cheap. Anyway I then discovered that the heaters are blowing cold(ish) air and not giving any hot air which the DPF specialist said I should have looked at before throwing money at the DPF.

The garage has stripped half the dash. All pipes which should heat up are heating up and they have now suggested either heater flap(s) not working or heater matrix and want me to spent a big chunk of money on a new heater matrix which is not a 100% guaranteed fix.

Any suggestion appreciated.

 

[elan2s]

Get someone with VCDS to do a full scan of the car, those on here with knowledge of these systems will be able to help you much more easily andf if there are errors in the AC/Heater system hopefully they will show up. Also which climate system do you have - 2 zone (temperature set by turning knobs) or 4 zone temperature set by buttons with digital display of temperature?

 

[Mazi]

Thanks for the reply. A full diagnostic scan has already been done and no faults relating to AC/HVAC have came up.
Its the 2 zone system I have with knobs.

 

[Mo-S3]

If the pipes to the heater matrix in the blower unit are getting hot then why have they suggested a new heater matrix? Even if a flap or 2 is faulty then it will show up on a scan and more so which ever position they are set to you will be getting hot air from a certain position.
Have they confirmed that the matrix pipes are hot and its the blower unit at fault or are the pipes cold and heat is confined tot he engine bay?
I have a 2 zone heater box with matrix unit, flaps, etc etc available if you need it as i removed mine when i did the 4 zone retrofit

 

[Mazi]

If the pipes to the heater matrix in the blower unit are getting hot then why have they suggested a new heater matrix? Even if a flap or 2 is faulty then it will show up on a scan and more so which ever position they are set to you will be getting hot air from a certain position.
Have they confirmed that the matrix pipes are hot and its the blower unit at fault or are the pipes cold and heat is confined tot he engine bay?
I have a 2 zone heater box with matrix unit, flaps, etc etc available if you need it as i removed mine when i did the 4 zone retrofit

Thanks for the reply. I am no mechanic so some of the stuff goes over my head. Pipes are hot. Heater matrix has been removed and full of brown crap and water is the colour of rust. They are saying its the matrix and if it doesnt cure it then I am in deep ****.

 

[Mazi]

They have suggested a new matrix and coolant flush with fresh coolant.
TPS is quite expensive for the matrix but I can get one aftermarket for reasonable money.

 

[Mo-S3]

If its full of brown crap and the water too then the tank in the engine compartment must be full of it too. I think you have another problem elsewhere... The coolant system is sealed and should stay a consistant pinkish colour. The brown colour is rust from ferrous materials that have rusted within the cooling system and blocked the passages in the matrix unit. the rust can also originate from minerals in tap water as tap water should NOT be used in cooling systems
Get it flushed and monitor the colour and make sure that they only use distilled water mixed with G13 to the correct ratio; i use 50/50 mix of genuine VW concentrated coolant.

 

[Mazi]

SOLVED
New genuine matrix fitted,
Whole system flushed and filled with VAG coolant.
Job done. Thanks for the replies

Sent from my SM-N950F using Tapatalk

 

[CoolAsIce]

I'd just like to add I had the same problem, 2012 A6 3.0tdi with 2 zone climate. I bought the car with 44k miles, full history and it was a very clean and well looked after car.

I soon realised the heater was virtually nonexistent. Being a mechanic myself, I rather look myself than take it back to the seller and go through hassle. But I soon found the coolant was very brown and almost sandy residue in the header tank.

I decided to pull the heater matrix out, which thankfully is actually a very easy job. It's a case of removing the glove box, remove the heater fan, undo the 2 hoses and slide the matrix out (a small plastic retaining clip has to be cut off to save a lot of work). I disconnected the matrix pipes in the engine bay, and blew the coolant out with compressed air, so that no coolant leaked into the car when removing the pipes at the matrix.

I spent some time flushing and cleaning the matrix, a ton of crap came out of it! Flushed the coolant in the engine and put it all back together. Also run some coolant flush through a few times.

A few months has passed, the heater is loads better now, and the coolant has stayed perfectly clear. However it could still be improved, so I think I'll have to replace the matrix eventually. So when I do that I think I'll flush the coolant again to make sure there's nothing to block the new matrix.

I just find it so strange how it got like that in the first place. The car has no signs of any work being done to it, still has original water pump, radiator etc so there's no reason why the coolant should have ended up by that. I wonder if it was a small bad batch of coolant from the factory? Really can't make sense of it.

This is the first post I've seen with someone having the same symptoms as I did. So I just thought I would add to it in case anyone is searching for the same fault like I was a while back!

 

[B5NUT]

Don't know if the PFL A6 has this but it does on the FL, there is a bag of silica in the coolant coolant reservoir, VW now use these bags as the silica content of the coolant is depleted over time, and if you lose the silica content of the coolant then corrosion can set in. So it my be worth replacing the coolant reservoir with a new one as they are only £27.

 

[CoolAsIce]

Don't know if the PFL A6 has this but it does on the FL, there is a bag of silica in the coolant coolant reservoir, VW now use these bags as the silica content of the coolant is depleted over time, and if you lose the silica content of the coolant then corrosion can set in. So it my be worth replacing the coolant reservoir with a new one as they are only £27.

Yes this was my initial thought, however mine does not have the silica gel.

 

[bx3m]

I'd just like to add I had the same problem, 2012 A6 3.0tdi with 2 zone climate. I bought the car with 44k miles, full history and it was a very clean and well looked after car.

I soon realised the heater was virtually nonexistent. Being a mechanic myself, I rather look myself than take it back to the seller and go through hassle. But I soon found the coolant was very brown and almost sandy residue in the header tank.

I decided to pull the heater matrix out, which thankfully is actually a very easy job. It's a case of removing the glove box, remove the heater fan, undo the 2 hoses and slide the matrix out (a small plastic retaining clip has to be cut off to save a lot of work). I disconnected the matrix pipes in the engine bay, and blew the coolant out with compressed air, so that no coolant leaked into the car when removing the pipes at the matrix.

I spent some time flushing and cleaning the matrix, a ton of **** came out of it! Flushed the coolant in the engine and put it all back together. Also run some coolant flush through a few times.

A few months has passed, the heater is loads better now, and the coolant has stayed perfectly clear. However it could still be improved, so I think I'll have to replace the matrix eventually. So when I do that I think I'll flush the coolant again to make sure there's nothing to block the new matrix.

I just find it so strange how it got like that in the first place. The car has no signs of any work being done to it, still has original water pump, radiator etc so there's no reason why the coolant should have ended up by that. I wonder if it was a small bad batch of coolant from the factory? Really can't make sense of it.

This is the first post I've seen with someone having the same symptoms as I did. So I just thought I would add to it in case anyone is searching for the same fault like I was a while back!

Hi there, I want to revive this topic, as it is currently "my turn" to fix this problem. First of all, do you know if there a difference between removing the heater core from the 2-zone climate unit vs the 4-zone? Did you have to remove something on the driver side? I've seen some images that suggest that you need to remove the driver's side dash panel cover, so you can clamp the hoses since they are fitted on the driver side, but you need to remove it through the passenger side.