A3 8V No Heat Diagnosis

[Twopips]

2014 2 litre TDI 43k and the heater just stopped. Back to the Audi dealer, plugged in £70 no answer, flush £300 not fixed, new matrix £700 not fixed, head gasket just replaced £1500 and still not fixed. This is with the Audi dealer, I simply asked them to fix my heater. Not sure where we will go from here. Apparently Audi uk are at a loss as well. Vor Sprung der technic ? So what’s next.... do I pay the bill ?

[DaleBrunton95]

Hello everyone, did anyone manage to get a fix for this? Having the same problem on my 2013 Audi A3, like warm from passenger side but cold on driver side, any ideas? 
help would be much appreciated 

[Rich83]

For anyone stuck with this problem in the future and come across this thread as i did.. I fixed mine today. Blocked heater matrix, i removed the two pipes coming out the car behind the engine at the nearest clips, (very fiddly and dificult to get to but got there in the end) flushed in through the outlet pipe using a garden hose, let some rad flush sit in it then flushed with hose again, refilled coolant and put back together.  (Replaced the spring clips with jubilee clips, just easier to get back on) And now heaters working perfectly.

The is a helpful video on youtube if you get stuck.

 

[Andrej]

Hey Guys I have the same kind of issues on my 2013 1.6tdi A3, local Bosch garage said it can be a can of worms and straight forward said we need a car for couple of days.

Below are my finings so far.

1.       My heating stopped working a few months after my Coolant pump and timing belt was changed (by local Bosch German car specialist garage)

2.       Changing the thermostat did not solve the problem (by my self)

3.       Looked at all the ventilation flaps and motors, all OK

4.       Back flushed the matrix (there was quite a lot of debris, which looked like a pulp from juice but harder). It resolved the problem for a little while. However, after two weeks the heating from the vents was not the same for left and right side of the car (I do not have zone heating), later it went cooler and cooler. If I drove through the city the heating worked however very faintly, if I went on motorway the heating was dead cold after 1 hour of drive.

5.       Back flushed the matrix again there oa flow through the matrix (garden hose pressure), flushed all coolant out, removed the thermostat and ran Holts Speedlfush and water through the system.

Now. When I was flushing and running water and cleaner through the system there was fair amount of heat coming through the vents, bear in mind the engine did not go above 50C. I have then put everything back together, replenish with fresh coolant and went for a test drive. Well, the heating was definitely there, faint but equal through the vents, however the engine did not warm up and it stayed 60C. Next day I swapped my new thermostat with the old thermostat, engine is now heating fine however the heating is very very faint.

Through out it all I had no performance problems, MPG stayed the same and the car/engine behaved normal, no OBD codes either. The only thing that did happen was gurgling noises behind the dashboard where the matrix is. The hose coming out of the cabin/matrix is cold while the hose going into the cabin/matrix is hot.

I have called my garage and they said it can be anything, from water pump (which they have changed), to clogged matrix, and they would need the car in for a few days.

What pushes the coolant through the core? Is it only the mechanically water driven pump?

Is the Heather support pump always running? As far as I can see the pump is sucking rather then pumping, since it is on the matrix outlet circuit.

Was the heating working when the water and cleaner was running through, because viscosity was less then coolants? Which would indicate the matrix is blocked or at least partially blocked?

If the check valve was closed constantly, should I not have cold inlet pipes to the matrix?

I know this is a lot of reading, however I would appreciate any thoughts.

Many thanks in advance, Andrej.

 

Many thanks in advance.

[RDeboys]

Hi I'm having similar problems with my Audi A3 1.6 2015 heater with it blowing cold air. However both pipes to and from the matrix are hot and when I have the blower on at a very very low speed I get hot air our of the vents.  As soon as I turn up the blower speed the heat disappears and the vents blow cold.

Does anyone have any ideas or advice?

Many thanks

[L22Kmd]

A lot of the problems listed above have been discussed on other forums and the common cause is the silica bag in the header tank splitting and blocking heater matrix resulting in a new matrix and flush required as a flush alone won't shift silica out of matrix. Just remove silica bag before it happens.

[Joel4motio]

On 12/31/2020 at 1:47 PM, RDeboys said:

Hi I'm having similar problems with my Audi A3 1.6 2015 heater with it blowing cold air. However both pipes to and from the matrix are hot and when I have the blower on at a very very low speed I get hot air our of the vents.  As soon as I turn up the blower speed the heat disappears and the vents blow cold.

Does anyone have any ideas or advice?

Many thanks

Manage to get anywhere with this, exact same issue.

[Vejgaard]

On 11/30/2020 at 9:18 PM, Andrej said:

Hey Guys I have the same kind of issues on my 2013 1.6tdi A3, local Bosch garage said it can be a can of worms and straight forward said we need a car for couple of days.

Below are my finings so far.

1.       My heating stopped working a few months after my Coolant pump and timing belt was changed (by local Bosch German car specialist garage)

2.       Changing the thermostat did not solve the problem (by my self)

3.       Looked at all the ventilation flaps and motors, all OK

4.       Back flushed the matrix (there was quite a lot of debris, which looked like a pulp from juice but harder). It resolved the problem for a little while. However, after two weeks the heating from the vents was not the same for left and right side of the car (I do not have zone heating), later it went cooler and cooler. If I drove through the city the heating worked however very faintly, if I went on motorway the heating was dead cold after 1 hour of drive.

5.       Back flushed the matrix again there oa flow through the matrix (garden hose pressure), flushed all coolant out, removed the thermostat and ran Holts Speedlfush and water through the system.

Now. When I was flushing and running water and cleaner through the system there was fair amount of heat coming through the vents, bear in mind the engine did not go above 50C. I have then put everything back together, replenish with fresh coolant and went for a test drive. Well, the heating was definitely there, faint but equal through the vents, however the engine did not warm up and it stayed 60C. Next day I swapped my new thermostat with the old thermostat, engine is now heating fine however the heating is very very faint.

Through out it all I had no performance problems, MPG stayed the same and the car/engine behaved normal, no OBD codes either. The only thing that did happen was gurgling noises behind the dashboard where the matrix is. The hose coming out of the cabin/matrix is cold while the hose going into the cabin/matrix is hot.

I have called my garage and they said it can be anything, from water pump (which they have changed), to clogged matrix, and they would need the car in for a few days.

What pushes the coolant through the core? Is it only the mechanically water driven pump?

Is the Heather support pump always running? As far as I can see the pump is sucking rather then pumping, since it is on the matrix outlet circuit.

Was the heating working when the water and cleaner was running through, because viscosity was less then coolants? Which would indicate the matrix is blocked or at least partially blocked?

If the check valve was closed constantly, should I not have cold inlet pipes to the matrix?

I know this is a lot of reading, however I would appreciate any thoughts.

Many thanks in advance, Andrej.

 

Many thanks in advance.

Did you ever find a solution?

[Andrej]

Yes.

At the end I replaced the heather matrix which was blocked (have not opened it up to see what was it blocked with). My coolant levels are now normal and the heating works, however I have replaced it with OEM part( Valeo is what was installed) and the design is not the best I should have gone and spent a little bit more money! <- Just as an advice from my experience, do a research and look if there is a better part for it. There is still some slushing sounds from the dashboard so there might be some air trapped there, I will back flush the matrix again when the weather gets a bit warmer and see if there is any more debris in the system. 

Hope this helps.

[James Auton]

Hi All,

I have a 2014 2.0TDI A3 and in the last few months i've had to top the coolant up from very low on a few occasions after long motorway runs. My heater lacks any significant temperature when it used to be hot within a few minutes due to the aux heater. There are no visible leaks and we've pressure tested the coolant system. It held 13psi for over an hour. Whilst the pressure test was performed the charge cooler was scoped. We thought it looked like small amounts of coolant residue however Darkside Devlopments have said it looks normal. 

I'm considering getting the EGR cooler replaced as i've read this is a common leak area. What do you think?

Did you find you were losing coolant with the blocked matrix with no obvious signs?

Grateful for a response as i'm at a loss and don't want to spend out replacing parts by guess work.

Thank you

[Steve Q]

6 hours ago, James Auton said:

Hi All,

I have a 2014 2.0TDI A3 and in the last few months i've had to top the coolant up from very low on a few occasions after long motorway runs. My heater lacks any significant temperature when it used to be hot within a few minutes due to the aux heater. There are no visible leaks and we've pressure tested the coolant system. It held 13psi for over an hour. Whilst the pressure test was performed the charge cooler was scoped. We thought it looked like small amounts of coolant residue however Darkside Devlopments have said it looks normal. 

I'm considering getting the EGR cooler replaced as i've read this is a common leak area. What do you think?

Did you find you were losing coolant with the blocked matrix with no obvious signs?

Grateful for a response as i'm at a loss and don't want to spend out replacing parts by guess work.

Thank you

Guessing you've looked at the head gasket. It could be the egr cooler. 

[Chris777]

Did anyone fix there issues please and how. Can see 5 or 6 people saying same issue but no one said if and how they sorted. Please help 

[Sid2020]

On 1/10/2025 at 1:13 AM, Chris777 said:

Did anyone fix there issues please and how. Can see 5 or 6 people saying same issue but no one said if and how they sorted. Please help 

Personally know a few people who have fixed a blocked heater matrix without stripping out the dash, all involved disconnecting coolant pipes from bulkhead and poking a powerwash  lance into the matrix pipes and blasting away until eventually water starts passing, apparently can take a while and involve a lot of blow black and beware that you could rupture your matrix If your power wash is too powerful. worth a try first if your prepared to replace the matrix anyway 

[Chris777]

Thanks Sid

I appreciate your message. 

Hoping to avoid replacing if poss. I have bought a cheap vacuum refill for putting the coolant back in and some Wynns Rad flush. It was a copart fixer upper and came with all coolant drained the lower coolant temp sensor on the corner elbow was popped out but not sure if the impact dislodged. Have read the matrix can gum up if coolant has drained and left to stand.? Think was only a few weeks but it's also a 14 plate. Was thinking like you said drain coolant. Then try and flush a few times. Where is the best point to flush the whole system and do you backwash or with the flow ?

Would you isolate the 2 matrix pipes and put the Wynn's just in that and flush or just in the header tank and run to temp? Getting no errors or codes and seems to take from the header but pulled the flow back in small pipe and can't see it coming back in. Not sure how possible as runs for a good 45 /60 mins before feeling too warm but no overheating warning on dash. I am quite new to this but keen to learn . Any help gratefully received.

[Sid2020]

For the matrix I would back wash it directly at the bulkhead, once happy reconnect and fill system with water, run upto temp making sure thermostat opens and electric fan kicks in. Turn interior temperature to hottest setting and leave fan off. Occasionally turn fan on to check if heat is present and encouraging flow. Leaving the fan on will slow down the heating process. Once your happy everything is hot I would pull a lower radiator hose to allow all water and muck to exit easy. Reconnect pipe and either repeat process again or fill with correct coolant. 
personally use any cleaning solution you want to clean the matrix but I would be careful putting anything into the complete coolant system apart from water and antifreeze 

[Chris777]

Ok thanks for that. Didn't know having the fan on would slow down the process. Struggling to get right to the bulkhead connection point with heat shield and location but seen a few people disconnect the hose connected to and flush through those 2? Would you use a pressure washer set to say medium? What is the part that hose connects to on the side of the engine please, a local garage said reduced or no flow is probably that and can swop all for about £500 inc parts? Is he meaning the water pump assembly do you think? Is this likely?

[Chris777]

Another quick question if I may. When draining how do you ensure getting as much out as poss, do you run up with pipe off to get out what's in the engine/stat open or is there another way?

I noticed when filling it took about 5 litres but online some say 8litres other places 10 litres for the 8v both quite a difference 

[Sid2020]

Ideally never run the engine without coolant so turn off before draining, you will never get all the coolant out so don’t worry too much, bottem hose is best as should drain down to Lowest point but pull as many as you want. if coolant is hot the thermostat should be open which would help

[Sid2020]

3 hours ago, Chris777 said:

Ok thanks for that. Didn't know having the fan on would slow down the process. Struggling to get right to the bulkhead connection point with heat shield and location but seen a few people disconnect the hose connected to and flush through those 2? Would you use a pressure washer set to say medium? What is the part that hose connects to on the side of the engine please, a local garage said reduced or no flow is probably that and can swop all for about £500 inc parts? Is he meaning the water pump assembly do you think? Is this likely?

Having the heater blower on is pushing air thru the matrix which has a cooling effect on the coolant inside so it slows the heating process down. Try a small Length of garden hose pushed into the matrix connector and put the power wash lance in the other end of hose, should aid access and reduce risk of damage by too much pressure. Just go back and ask the garage to clarify what parts are getting replaced for the £500, perfectly acceptable question that they should be happy to answer

[Chris777]

Ok thanks

Does the 1.4 TFSI have an auxillary pump? Could this be at fault? How do you go about diagnosis when no errors are logged at all. Garage said 'it's an educated guess' from others he's done for £500 I'd want a little more if any way poss

[Chris777]

Looks like Water pump/stat assembly is on that side and what is referring to. It's about £190,for OEM which is also about what he was saying with £300 ish labour for 3-3.5 hrs

[Sid2020]

Done a water pump On a 2017 A1 1.4 tfsi just last Saturday on my drive, water pump on gearbox and driven from the cam shaft. Very easy job and would encourage anyone to to do it themselves, basic tools required are basic socket set,  torx  sockets and 10mm Allan key socket with torque wrench, plumbers wrench for coolant pipes. Audi water pump comes complete with thermostat housing and thermostat. Also order a new belt for it

[Sid2020]

1 minute ago, Sid2020 said:

Done a water pump On a 2017 A1 1.4 tfsi just last Saturday on my drive, water pump on gearbox and driven from the cam shaft. Very easy job and would encourage anyone to to do it themselves, basic tools required are basic socket set,  torx  sockets and 10mm Allan key socket with torque wrench, plumbers wrench for coolant pipes. Audi water pump comes complete with thermostat housing and thermostat. Also order a new belt for it

It’s not timed, your not interfering with any of the engine timing so don’t worry, from memory the 10mm hex is 30nm and is applied to pump housing while The torx’s or tightened. The 30nm on the 10mm hex is not a bolt, it’s on the pump Housing and is used to set the belt tension. Strange idea I admit 

 

[Chris777]

Thanks Matt

How likely do you think is this?.how do I diagnose for sure? No noise coming from it.

Getting really hot input pipes to rad and matrix but both outputs are slightly warm at best.

 

[Chris777]

Getting no leaking or check engine light, no faults at all.