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A/C help. Air Conditioning only works for 5 minutes


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#1 urquhartps

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Posted 19 June 2017 - 09:23 AM

Hi All.

 

I'm trying to get to the bottom of an air conditioning problem I've had since buying my car a few years ago. I probably attempt to fix it every year when it gets hot. The car is actually an Audi A3 8L but it should be the same platform and the Audi forums are pretty useless so I'm hoping to find some experts in here instead that can help me before I melt.

 

Engine is a 1.8T.

 

I've just had the a/c regassed and it holds pressure. When I switch the a/c on, everything seems to work. The compressor kicks in and the revs change. The fan speed increases and the a/c rad fan also works frequently. 

 

If I've just started the car from cold and switched the a/c on, I get cool air for about 5 minutes. Then it slowly fades to hot air. The compressor still seems to be engaged. The air does not return to cool for a number of hours - almost as if it depends on the engine being cold or the a/c not being used for a while.

 

I have Vag-Com but there are no faults in the HVAC. I had suspected there may be an issue with a temperature sensor perhaps but everything else seems to work ok. The dash seems to report the outside temperature correctly.

 

What could it be?

 

Thanks in advance,

Paul




#2 northpole

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Posted 19 June 2017 - 11:23 AM

Do you have climatronic or is it airconditioning meaning you have to set the temperature with knobs instead of a digital display panel.

If you have climatronic it has uses 2 temp sensors the one for outside and one in the dash it is located in the top middle of the vents.

The reason why I ask is because although they have similar workings the climatronic has more to go wrong

#3 urquhartps

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Posted 19 June 2017 - 11:28 AM

Do you have climatronic or is it airconditioning meaning you have to set the temperature with knobs instead of a digital display panel.

If you have climatronic it has uses 2 temp sensors the one for outside and one in the dash it is located in the top middle of the vents.

The reason why I ask is because although they have similar workings the climatronic has more to go wrong

Sounds like I must have climatronic. The panel looks like this one: 

panel-klimatyzacji-climatronic-audi-a3-a



#4 northpole

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Posted 19 June 2017 - 11:31 AM

Right you've got climatronic.... could be that the dash sensor is not giving proper readings... a motor to move the wind direction could be stuck or jammed, or the panel itself has a problem.... all stated problems will turn off the cooling. So you will have to check every bit of the system separately

#5 urquhartps

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Posted 19 June 2017 - 11:36 AM

Right you've got climatronic.... could be that the dash sensor is not giving proper readings... a motor to move the wind direction could be stuck or jammed, or the panel itself has a problem.... all stated problems will turn off the cooling. So you will have to check every bit of the system separately

Ok, thanks. That gives me a new place to look. Would these issues normally be logged as error codes though? I'll take another look with my cable later on.



#6 northpole

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Posted 19 June 2017 - 11:38 AM

They should but it doesn't always log it especially not if the system has had the same problem for a while.

#7 urquhartps

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Posted 19 June 2017 - 12:35 PM

Still no errors found. I've pulled apart the centre console a little bit and there is a temperature sensor just above the climatronic box with its own air feed. It is working as I can see it in Vag-com which calls it 'interior temperature'.

 

There is another reading called 'central outlet' which is reading 0. So either I have a broken sensor (where is it?) or my car doesn't use this.

 

Northpole, you mentioned above that there is 'one in the dash it is located in the top middle of the vents'. Any ideas how to locate this sensor? 

 

Cheers,

 

Paul



#8 northpole

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Posted 19 June 2017 - 01:02 PM

It is in that position in the golf mk4.... the next one should be outside somewhere near the front bumper....

#9 BigBang

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Posted 19 June 2017 - 02:31 PM

From my own experience the codes may not show in vagcom, but will show in the self diagnostics of the climatronic, don't know if it's the same as the the mk4 but may be worth googling your car and climatronic self diagnostic and find out which combination of buttons you press to get it up

#10 urquhartps

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Posted 19 June 2017 - 02:53 PM

From my own experience the codes may not show in vagcom, but will show in the self diagnostics of the climatronic, don't know if it's the same as the the mk4 but may be worth googling your car and climatronic self diagnostic and find out which combination of buttons you press to get it up

 

I've been experimenting with that also. It's the same on my car I think. Hard to tell if anything is wrong from all the readings though. Only thing i'm a little suspicious of after checking all the codes is a sensor called G109. This seems to be reading 43C which may be correct in this weather or may be a fault. It also reads 255 when checking the digital value (Code 7 in the climatronic hidden menu) - I think 255 this looks suspiciously like a max value in 8 bit but I have no idea where this sensor lives just yet.

 

 

Do you know what sort of code I should be looking for in the climatronic?



#11 BigBang

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Posted 19 June 2017 - 03:54 PM

Does it through up any fault codes through the climatronic screen?

#12 northpole

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Posted 19 June 2017 - 03:58 PM

http://mr-fix.info/a...-menu-a2-a3-a4/

That should help you get the fault out of the climatronic

#13 urquhartps

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Posted 19 June 2017 - 04:46 PM

Does it through up any fault codes through the climatronic screen?

No fault codes (entry 1 in the climatronic menu).



#14 urquhartps

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Posted 19 June 2017 - 04:50 PM

http://mr-fix.info/a...-menu-a2-a3-a4/

That should help you get the fault out of the climatronic

Yep, that's what I've been using but no error codes. Like I said, the only slightly suspicious one is option 7 'value of Temperature Sensor At Fresh Air Blower (G 109)' which reads 255. That sounds like a maximum reading to me which is perhaps unlikely or incorrect. But It's not clear where this sensor is.

 

I've already got a new exterior sensor but I think it's probably fine as it reads about right.

 

Is it common to have faulty temperature sensors preventing the climatronic from cooling? Can anything else cause the symptoms I described or does this definitely sound temperature sensor related? If so, I'll keep testing them.



#15 northpole

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Posted 19 June 2017 - 05:01 PM

That is usually the thing that goes wrong.... apart from the clutch on the compressor or gas leaks....

So worst case would be that you'll have to dismantle the system to get to it.... this means taking the dashboard apart.

Because if it is were I think it is than it would be in the tunnel where the cooling element sits.....

Big job




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