No hot air, most of the time. All vents, controls working, in and out hot.

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mwilson

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Hi,
Search brought up a few options but wanted to check.
Audi A4 Avant from 2003.
All climate control / air con controls are working.
All vents pumping out air.
The only problem is...sometimes it's warm, most times it's not.

I've read it could be matrix or motor but as it is sometimes going hot wondered...

So it works and it doesn't work. More not then does.

Any suggestions?

In and out pipes both warm, low to high controls all blow at different levels, all vents blow as they should.
System has been checked and small bit of air flushed out.
Fuses checked.

Thanks.
 
Sounds like you've done all necessary testing

I'd change the motor first

One thing to check would be for wet foot wells, that would indicate a leaking matrix
 
Thanks Pops. I'll check the footwells tomorrow morning..have not noticed any wetness.
Then find a Audi specialist about the motor change...not a diy job I imagine....quite a few motors in there from what I read.
 
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If the matrix pipes are only warm it cant supply hot air so the system is staying too cool probably cos the stat is failing or sticking sometimes.Blocked matrix would be constant but the intake pipe would still get hot .I would change the stat first.Does it get to 90 quickly and stay there?If not that points to the stat
 
Thanks Mike. Gets to 90 and stays constant so I guess that points to stat being ok.
I'd love to be able to at least try a fix myself at first but may call the local(ish) audi specialist today...
 
The A4 heater motors are easily accessible, remove the glovebox for the passenger side ones and remove the drivers knee bolster for the drivers side (obviously) If you're sure the matrix and thermostat are okay I would try a reverse flush of the heater matrix.
 
QuattroCalum said:
The A4 heater motors are easily accessible, remove the glovebox for the passenger side ones and remove the drivers knee bolster for the drivers side (obviously) If you're sure the matrix and thermostat are okay I would try a reverse flush of the heater matrix.
Click to expand...
Thanks. As all of the vents are blowing as they should,just not hot, how would I know which of motors is faulty?
 
QuattroCalum said:
Hot and cold are red and blue coloured.
Click to expand...
Thanks. That make sense. Once I see the hot (red) motors, on both sides as no hot on driver or passenger side, is it visually / audibly obvious if one is not working?
 
You should be able to see and hear the motors working, have the ignition on and adjust the heat all the way up and watch/listen for movement if that side is okay, move to the other side and do the same. Are the coolant pipes on the engine considerably warmer than the heater matrix hoses?
 
QuattroCalum said:
You should be able to see and hear the motors working, have the ignition on and adjust the heat all the way up and watch/listen for movement if that side is okay, move to the other side and do the same. Are the coolant pipes on the engine considerably warmer than the heater matrix hoses?
Click to expand...
It was my local garage that checked the pipes etc for me and reported back in and out pipes both hot and they flushed system to remove small air blockage. They suggested motor or matrix and best to see audi specialist to make sure first. Didn't want me to me to sen money on new motor if not needed, etc.
So from their report I'm assuming pipes both hot etc, but coolant pipes may be very different place to the 2 in / out heater matrix hoses?
Can you tell I'm new to this :)
 
Have a look at this video on youtube, it's on a Passat but the setup is very similar
 
Motor is an easy check

Glovebox is 7 bolts I think, mine were all 8mm
You can then see motors in action, that'd would be what I would do, I'd also see it not hear it I case motor moves but arm is snapped or it's not moving enough etc etc.
That's good thing to eliminate
 
Over last few days the system has started to blow slightly warm intermittently. But then cold again.
So I've removed glove box to see motors etc in action.
Looking at attached pictures, when using all buttons / controls on both sides of the climate control panel they all do something at some point with exception of the red lever which does absolutely nothing at any point....I'm hoping the red arm mens hot air motor?
So my very basic assumption from my very basic testing method is the motor with the red arm attached is not working and needs replacing.
I did also remove driver side knee cushion but could not see motors on that side...as motors on passenger side were activated by both passenger and driver side controls, I assume that is how it should be.
IMG 5611
IMG 5612
I'm guessing there is a single large flap motor on the drives side but can look again for that if need be.
Marc
 
Ah, none on the drivers side, sorry that was my assumption. Good news, replace the red one and you should be nice and toasty again.
 
QuattroCalum said:
Ah, none on the drivers side, sorry that was my assumption. Good news, replace the red one and you should be nice and toasty again.
Click to expand...
So the red one, and other two in close proximity, are heater position motors I believe? So the red arm motor not working means there is heat but is not getting sent into right position to come through vents?
 
Once replaced do you know if I need to perform some kind of 'reset' that I have seen mentioned in some threads? Thanks.
 
Best to scan with vcds which would show up dodgy flap motors. There is also a temp motor on the driver side up behind the dash and temp sensors in the left and right side air vents.

Sent from my SM-G900F using Tapatalk
 
Ralphthemouth said:
Best to scan with vcds which would show up dodgy flap motors. There is also a temp motor on the driver side up behind the dash and temp sensors in the left and right side air vents.

Sent from my SM-G900F using Tapatalk
Click to expand...
Thanks, I'm going to replace the non working red tab motor tomorrow and see if that fixes it...£20 repair job if it has!...unfortunately the car may well have much larger problems that the lack of hot air...
 
ive got nearly the same issue with mine. since i changed the thermostat. i have to keep bleeding the system. andf ive also notiched that i get heat when the water level in the expansion tank goes below the max. mark. still not got the bottom of this issue yet.
 
Neil.It may be that you have a leak which lets the air in and is keeping the pressure down
 
I've replaced non working red arm motor with a working one but whilst the motor and arm move now still no hot air.
Wondering if I need to reset the heating system in some way?
Can't see any motors on driver side.
Not sure I'm up to other suggestions.

Otherwise the car is going in after new year for some auto gearbox juddering issues so can get the heating looked at then also.
 
You should be able to see and hear the flap to the matrix moving high in the rear of centre of the dash.Odds on the matrix is blocked.Hope the autobox is OK.Is it multitronic?
 
After fixing the motor I have now heard much more movement from behind the centre dash / vents.
I'll look back through thread about cleaning etc matrix.
Re gearbox yes it's a cvt multitronic... imminent doom from what I can gather...
 
Do you get heat from one side only or nothing all round? Don't want to tell you how to suck eggs, but hold the 'auto' button down for about 5 secs and then you can control the temp of both sides from the drivers side. It makes it easier to check the temperature differences. I had a similar problem when I only had heat on the passenger side. I changed the drivers side temp flap motor (right up above the clutch pedal on the side of the centre console) and then noticed when the temp went above 21c the motor suddenly shut off and I got cold air. I ran through basic settings on vcds and it still wouldn't sort the issue. I ended up having to slowly increase the temp a few degrees at a time, until i finally got it up to high without the motor tripping back to cold. It's been working fine since then. (5 months).
Don't know if that's any help to you but it's something to look for if you get stuck.

Sent from my SM-G900F using Tapatalk
 
Maybe the box just needs a good service.That would be my priority then have a go at the matrix
 
Agreed. Not doing anything until auto gearbox looked at. Repair might cost more then car did a few months back!
 
Mike B said:
Neil.It may be that you have a leak which lets the air in and is keeping the pressure down
Click to expand...
hi mate the funny thing is i cannot see any leaks on the floor. so iam lost for where to look next. there is no oil in the water and vice versa.
 
Long drive today and once car heated up, long front demist and 2 top demist both pouring out hot air, but all flap vents still cold at same time. Then 3 hours into journey flap vents air came out hot also! All very random!
 
this issue of mine has taken another twist. while i was out yesterday. the temp gauge dropped from 90 down to the 70 mark, and got loads of hot air in the car. and the same today. went to london and back sat at nearlly 70 degree and still got heat in the car. this is very strange.
 
Hi neil.Once warmed up you will still get heat at 70 but the stat is not keeping it at 90.My sons TT was doing just this recently and a new stat fixed it.Are you topping up much?That would indicate a leak.
 
Mike B said:
Hi neil.Once warmed up you will still get heat at 70 but the stat is not keeping it at 90.My sons TT was doing just this recently and a new stat fixed it.Are you topping up much?That would indicate a leak.
Click to expand...
hi mate it is a new thermostat. and no need to top it up.
 
Was the stat genuine?Have you tried a new CTS?Dont you need to top up after bleeding?
 
Or maybe the pressure cap isnt sealing fully?
 
hi mate what is a cts. also it is a new expansion tank and pressure cap and yes it was an oem stat.
 
Neil the cts is the coolant temp sender.It affects the running temp .Easy to switch but good one not cheap might be worth a try
 
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