A4 heater, only blowing cool air
Discussion
I have a 2005 A4 Avant B7 and only blows cool/tepid air when on high setting, this started today.
Could it be an air lock as it's just had a new cylinder head a couple of weeks ago, if it is how do you get rid of an air lock ?.
Or could it be something else, your thoughts would be appreciated.
Could it be an air lock as it's just had a new cylinder head a couple of weeks ago, if it is how do you get rid of an air lock ?.
Or could it be something else, your thoughts would be appreciated.
Could be but unlikely, check the coolant level, air locks tend to eventually end up in the tank. If the levels way down then possible. Or it could be a coolant leak
More likely though to be a flap motor not moving and closing off the cool air to allow the hot air into the cabin. 1/2 hour diagnostics at a place will tell them which one. Depends on which one as to how much the labour is to fit it and reset the basic settings.
More likely though to be a flap motor not moving and closing off the cool air to allow the hot air into the cabin. 1/2 hour diagnostics at a place will tell them which one. Depends on which one as to how much the labour is to fit it and reset the basic settings.
Rich_W said:
Could be but unlikely, check the coolant level, air locks tend to eventually end up in the tank. If the levels way down then possible. Or it could be a coolant leak
More likely though to be a flap motor not moving and closing off the cool air to allow the hot air into the cabin. 1/2 hour diagnostics at a place will tell them which one. Depends on which one as to how much the labour is to fit it and reset the basic settings.
All the vents are blowing cool air, what would cause all the flap motors to fail, a fuse or could the heater matrix be blocked ?.More likely though to be a flap motor not moving and closing off the cool air to allow the hot air into the cabin. 1/2 hour diagnostics at a place will tell them which one. Depends on which one as to how much the labour is to fit it and reset the basic settings.
Edited by flatsix3.6 on Sunday 9th February 14:25
flatsix3.6 said:
Rich_W said:
Could be but unlikely, check the coolant level, air locks tend to eventually end up in the tank. If the levels way down then possible. Or it could be a coolant leak
More likely though to be a flap motor not moving and closing off the cool air to allow the hot air into the cabin. 1/2 hour diagnostics at a place will tell them which one. Depends on which one as to how much the labour is to fit it and reset the basic settings.
All the vents are blowing cool air, what would cause all the flap motors to fail, a fuse or could the heater matrix be blocked ?.More likely though to be a flap motor not moving and closing off the cool air to allow the hot air into the cabin. 1/2 hour diagnostics at a place will tell them which one. Depends on which one as to how much the labour is to fit it and reset the basic settings.
Regarding the heater, there's 1 motor that does the whole system hot to cold. So if it's stuck in cold position, it won't matter where you direct the air. Vents, screen, feet it will come out cold. I would be amazed if the matrix was blocked very very rare. If the coolant is ok then the problem is with the hvac system.
btw They look like this
This is an A3 one but they are all similar.
Rich_W said:
I would be amazed if the matrix was blocked very very rare. If the coolant is ok then the problem is with the hvac system.
Not rare at all. Very common in fact. The 'anti burst' nature of these matrices seems to cause them to clog very easily since the coolant flow can avoid the 'radiator' part of the matrix. Certainly on the B6, any form of air lock can also cause the heater to stop working and they can be a pain to bleed properly. The heater has a separate bleed point.Are you getting any heat at all? If you're getting lukewarm air out of the screen vents then I would blame the matrix, although the sudden nature of the problem does make it sound a little unlikely.
Hi there ..I had this problem on my a4 2.0 TDI..on mine there was an air lock in my matrix radiator..to cure this I run the car and got warm then find the 2 rubber hoses that go into the car for the matrix..mine are dead centre under bonnet at back to left of battery..anyway undo the clip and pull it back ..then if you look on the rubber hose there is a small like pin hole in it around an inch back on the rubber hose ...gently pull back the rubber hose until the pin hole is clear of the metal pipe and air will hiss out ( I left my engine running).. When the air stops coming out and water squirts through the pin hole your done.. Tighten up the clip again !.. Please do at your own risk and be careful ..1 ..the metal pipes from the matrix radiator are soft aluminium and damage easy when trying to remove rubber hose and are usually very tight 2.. Be careful of hot water ...this worked for me after changing thermostat and temp sensor and still cold blowers :-) p.s the top was the only one I undid and was the tlreturn to engine ..hope this helps everyone ...I have heard stories of head cracked ..water pump gone etc.... All along was an airlock stopping hot air circulating for heating ..
Thread resurrection! Apologies.
Have B6, cold air blowing. Blows warm air when revved.
The matrix has been cleaned out, a lot of crap came out apparently, and my guy had the system blowing hot after that, until he engaged the aircon, then it went cold again. The pipes leading out the engine into the system can be red hot, but no heat internally.
Any other ideas? A US Audi/VW site has suggested coolant flush then compressed air, but not sure about that.
Have B6, cold air blowing. Blows warm air when revved.
The matrix has been cleaned out, a lot of crap came out apparently, and my guy had the system blowing hot after that, until he engaged the aircon, then it went cold again. The pipes leading out the engine into the system can be red hot, but no heat internally.
Any other ideas? A US Audi/VW site has suggested coolant flush then compressed air, but not sure about that.
Just sharing my own experience on this topic. Had the thermostat replaced on my 2005 1.9TDI (manual) a week ago, then 3 days ago, having driven 6+ hours, the aircon stopped blowing out hot air. Have tried pulling back hose to/from heat exchanger to allow air out today and lifting reservoir so it's above the pipe, did eventually get some coming out but a bit sporadic and no hot air yet yet, but will try a few more times over next few days as another thread suggested.
Other symptoms, it will blow out hot/warm air for a short while if fan has been off for a while which seems to suggest some heat is getting in to the exchanger, albeit slowly. The bottom of the 2 pipes to/from the heat exhanger/matrix is hot (feels full of hot water), but top pipe is cold/empty so again, seems like water flow to/from heat exchanger is the problem (rather than flap that control air flow over the heat exchanger/matrix).
Garage couldn't diagnose, best suggestions were i) the heat exchanger/matrix is blocked (but this has been a sudden onset, not slow build up as some threads suggest is common with blockage); or ii) the water pump is faulty (but the engine temperature never goes above 90c and the pump was only replaced 2 years ago).
Will see if it improves in next few days with regular bleeding and update post.
Can anyone advise if I need to have the engine running whilst bleeding or will it bleed okay without? Also, better to do it hot or cold? (Obviously being careful if hot!)
Thanks
Other symptoms, it will blow out hot/warm air for a short while if fan has been off for a while which seems to suggest some heat is getting in to the exchanger, albeit slowly. The bottom of the 2 pipes to/from the heat exhanger/matrix is hot (feels full of hot water), but top pipe is cold/empty so again, seems like water flow to/from heat exchanger is the problem (rather than flap that control air flow over the heat exchanger/matrix).
Garage couldn't diagnose, best suggestions were i) the heat exchanger/matrix is blocked (but this has been a sudden onset, not slow build up as some threads suggest is common with blockage); or ii) the water pump is faulty (but the engine temperature never goes above 90c and the pump was only replaced 2 years ago).
Will see if it improves in next few days with regular bleeding and update post.
Can anyone advise if I need to have the engine running whilst bleeding or will it bleed okay without? Also, better to do it hot or cold? (Obviously being careful if hot!)
Thanks
- Update: Finally managed to get the rubber pipes off the heating exchanger/matrix connections at top of engine bay and flushed the matrix which seems to have rectified the problem (not uber-hot air yet but suspect a bit more bleeding and will be there). The hardest part was getting the pipes off as they probably haven't been removed in 10yrs so had corroded on. The Sealey VS352 Hose removal tool was a godsend!
Edited by BlueRinse05 on Sunday 1st January 11:44
Tonsko said:
Thread resurrection! Apologies.
Have B6, cold air blowing. Blows warm air when revved.
The matrix has been cleaned out, a lot of crap came out apparently, and my guy had the system blowing hot after that, until he engaged the aircon, then it went cold again. The pipes leading out the engine into the system can be red hot, but no heat internally.
Any other ideas? A US Audi/VW site has suggested coolant flush then compressed air, but not sure about that.
Sounds a lot like a Water pump or thermostat to me. Have these been checked?Have B6, cold air blowing. Blows warm air when revved.
The matrix has been cleaned out, a lot of crap came out apparently, and my guy had the system blowing hot after that, until he engaged the aircon, then it went cold again. The pipes leading out the engine into the system can be red hot, but no heat internally.
Any other ideas? A US Audi/VW site has suggested coolant flush then compressed air, but not sure about that.
Tonsko said:
The engine isn't overheating, so the water pump should be ok, no? Will maybe focus on thermostat for the next attempt, thanks!
Don't the impellers tend to fracture and effectively spin freely on the spindle on these water pumps? This also happened to mine. It ran ok for a while (but with no water flow through the matrix) until it eventually overheated on the way to work one morning after going up a long steep hill. Was glad to see the back of that money pit.The matrix has been flushed, coolant seems to be moving ok.
Drive it a bit more now (it's the other half's car mostly) and if you have it on low power (i.e. one or two bars) then you get warmth. Any more blow and it starts cooling down - presume because there's not enough heat exchanging going on.
Does this suggest that the matrix is buggered? I'm told it's a , as the dash has to come out
Drive it a bit more now (it's the other half's car mostly) and if you have it on low power (i.e. one or two bars) then you get warmth. Any more blow and it starts cooling down - presume because there's not enough heat exchanging going on.
Does this suggest that the matrix is buggered? I'm told it's a , as the dash has to come out
Hi all. Having same issue with my A4 B6 1.9tdi. Replaced thermostat,sensor and only this week I decided to check the pump. It was fine but when I was in there I fitted new genuine timing belt kit including pump. Car can idle from cold with no heat until you rev it up and down. The the heat will work as normal all day until I drive it hard and temp needle will start heading past 90' very quickly. I've also noticed that after a drive the coolant level will have went down in reservoir and if I open cap there's there's a sucking pressure and coolant returns to maximum level
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