# AC is not working



## Chunki84 (Dec 18, 2008)

No cold air. 
Clutch is not engaged. 
I changed coolant temp. sensor, temperature switch located on high side of ac line. fan control modules and checked all fuses. 
No luck. 
I disconnected the connector attached to AC today and wired with multimeter and found no voltage(when I turned on cold air). 
I have spare air compressor but since no voltage, I don't think I need to replace the air compressor yet. 
Any suggestion?? 

audi tt 2001q amu


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## darrenbyrnes (Jan 4, 2005)

Welcome to the club...


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## 20v master (May 7, 2009)

Run a hot wire straight to the fan motor. Could be that the fan motor has gone out. If it won't turn on, then your AC compressor won't clutch on.


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## Charlie_M (Mar 23, 2011)

Chunki84 said:


> No cold air.
> Clutch is not engaged.


 Long shot, but does your outside temp in the cluster read OK? If that reads below about 37F (I think), it will keep the AC from kicking on. 

There are also lots of codes you can get to from the AC control panel to diagnose the problem; check the FAQ for details (sorry I don't have a link handy). 

Also there is a cooling/AC FAQ on the 1.8T board here: http://forums.vwvortex.com/showthread.php?5265213-FAQ-Radiator-Cooling-Fan-and-A-C


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## Chunki84 (Dec 18, 2008)

what is fan motor? 
and what is hot wire???


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## Chunki84 (Dec 18, 2008)

climate control panel shows current temperature, is it mean out side temperature cluster works ok? 
If not, how to trouble shoot out side temperature cluster?


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## Charlie_M (Mar 23, 2011)

Chunki84 said:


> climate control panel shows current temperature, is it mean out side temperature cluster works ok?
> If not, how to trouble shoot out side temperature cluster?


 Fan motor: he means fans behind the radiator. They should be on whenever AC is running 

The red panel in instrument cluster: does it show outside temperature OK? 

Accessing climate control diagnostics & codes: 
http://www.wak-tt.com/tt/climatecontcodes.htm and 
http://www.youtube.com/watch?v=gU6aiySTHpU


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## Charlie_M (Mar 23, 2011)

Chunki84 said:


> what is fan motor?
> and what is hot wire???


 (Honestly if you have to ask you probably should get an experienced helper) ... But hot wire refers to a 12V wire direct from battery. Be sure to put a fuse in it for safety, and you need to look up which of the three terminals to power!


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## Chunki84 (Dec 18, 2008)

what amp of fuse can you suggest?


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## Chunki84 (Dec 18, 2008)

thanks for link. 
it will be very helpful. 
Never knew climate module can do that.


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## Chunki84 (Dec 18, 2008)

I checked with climate control unit, the temperature shows fine. 
32c degree today. 
Can I run hot wire straight to the air compressor? 
I have extra connector that can connect with air compressor. 
I can extend wire to battery and want to run if the clutch is engaged. 
One more thing, the connector, I can not figure out which one goes positive, 
there are numbers 1 and 2. and the color of wires are pink and green.


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## Chunki84 (Dec 18, 2008)

just checked fan motors. 
Both fans work fine low speed and high speed when I run with hot wire. 
I checked voltage of the connector that attached to fan switch both way can be read around 11v. 
How can I troubleshoot fan switch is working? 
I don't mean fan control unit. 
I mean fan switch that attached on radiator.


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## Chunki84 (Dec 18, 2008)

I wired compressor clutch straight to battery today. guess what? 
Clutch works and cold air blew in to the car. 
so, it's not a clutch.. 
It probably some sensor or switch. 

that's what I done so far, 
1. both fan motors are working slow or high. 
2. I changed coolant temperature sensor. 
3. I changed a/c switch located on high port of ac pipe. 
4. I changed fan control unit three times. 
5. I checked all fuses. 
6. I checked voltages that go to fan switch on radiator. both voltage around 11v. 
7. I checked temperatures from climate control unit, all temperatures can be read find. 
8. No voltage found connector that attached to compressor clutch even I set lowest desired 
temperature. 
9. If I wire compressor clutch with battery directly, cold air blow in to car. 

What's wrong;;;


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## Charlie_M (Mar 23, 2011)

Chunki84 said:


> I wired compressor clutch straight to battery today. guess what?
> Clutch works and cold air blew in to the car.
> so, it's not a clutch..
> It probably some sensor or switch.
> ...


 Re-read the link I posted above: http://www.wak-tt.com/tt/climatecontcodes.htm 

Specifically, check the 'compressor off' code on the climate control display: "OBD Channel 52 - A/C Compressor switch-off codes ... If an A/C compressor switch-off condition exists, a segment of the "88.8" display, indicated below as an alpha-numeric code, will illuminate. " If the FCM is OK, It will tell you exactly why the compressor is not working (ie, which sensor may be bad). 

Did you check all of the fuses on top of the battery? Look underneath; they can be burned and make no contact, even if they are not 'blown'.


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## Chunki84 (Dec 18, 2008)

I did and it just showed just one single "0". 

I checked fuses one the top and everything is fine and 
I checked fuses box if there was burned spot. everything looks fine. 
I checked with voltage meter for lines and I can voltages every end of lines.


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## darrenbyrnes (Jan 4, 2005)

FWIW: I swapped and reseated the 3 green fuses on top of the battery and reseated the High Pressure switch on the A/C HP line and now I got my A/C to work. I still need a recharge, but it wasn't blowing completely hot air at me... 

:thumbup::thumbup::thumbup:


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## Jayizdaman (Apr 18, 2005)

I am also diagnosing my AC and using the methods that people have been suggesting in this thread but I am think my CC software is different or at least not reading the way as it should. Certain readings seem non-sensical. For example 52C which should give me error codes, just produces a 16. 29C (AC compressor speed in RPM) always says 3 regardless of setting. 

22	Cycle condition of A/C Refrigerant High Pressure Switch (F 118) gives me a 1 
23	Cyclings of the A/C Refrigerant High Pressure Switch (F 118) gives me a 0 

Do these make sense to anyone? 

The other codes I get with 1C are: 4.4, 5.2, 11.7, 15.3 which appear to be weird sporadic blocks in ducts or the first one (4.4) which is a short in my sensor. 

Now I know some people have said that if the CC reads that the temp is too low it won't kick the AC on no matter what, but my Temp readings have always been high. It's 70 degrees out now and my Dash says 83 degrees F. 

Very Odd


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