# air con not working - 00792 - A/C Pressure Switch (F129)



## Jettacli (Jan 13, 2005)

2002 jetta mk4
My air con suddenly stopped working , the pump doesn't kick in and the cooling fans don't go to high speed with the air con on. the fans work normally with no engine overheating.
This is the code that I get
VAG-COM Version: Release 311.2-N
Control Module Part Number: 3B2 907 044 C 
Component and/or Version: CLIMATRONIC C 1.0.0
Software Coding: 01000
Work Shop Code: WSC 31414
1 Fault Found:
00792 - A/C Pressure Switch (F129)
35-00 - -
The climatronic's fuse also fused out , I have managed to stop the fuse blowing by disconnecting the A/C Pressure Switch.
I found this url: http://www.ross-tech.com/vag-c...4.lbl
by watching the measuring blocks I get these results:
Component: A/C Heating Electronics (J255) (#01) - Climatronic
measuring block 001,1
on econo mode: 6 = Compressor OFF by ECON Button - correct
on auto mode: 1 = Compressor OFF by Pressure Switch (F129): Refrigerant Pressure too High
after about 30 seconds it changes to:
3 = Compressor OFF by Pressure Switch (F129): Refrigerant Pressure too Low
I suspect the switch is faulty but don't want to change it until I'm reasonably sure , If i take the switch out I loose all the gas as well and thats going to cost me a re gas.
I also think climatronic's fuse blowing is because the A/C Pressure Switch 
is shorting out , but again I'm not sure.
any help , thoughts appreciated
thanks

http://****************.com/smile/emthup.gif


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## Theresias (Feb 11, 2004)

*Re: air con not working - 00792 - A/C Pressure Switch (Jettacli)*

http://wiki.ross-tech.com/index.php/00792
You may want check the repair manual for instructions too...


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## vwemporium (May 27, 2002)

*Re: air con not working - 00792 - A/C Pressure Switch (Jettacli)*

http://forums.vwvortex.com/zerothread?id=1542694


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## Jettacli (Jan 13, 2005)

*Re: air con not working - 00792 - A/C Pressure Switch (vwemporium)*

thanks guys
also found this , describes my problem exactly:
http://www.wavenetmx.net/switchf129.pdf
Output on printer of VAG 1551
Scan Tool (ST)
Possible cause Corrective action
00792 3224
A/C Pressure Switch -F129- Display occurs only vehicles
up to model year 2001
Short circuit to
Ground /SP - Open circuit in wiring
between A/C Pressure
Switch -F129- and A/C
Control Head -E87-.
- Activation of Coolant Fan -
V7- (step 1) malfunctioning.
- Condenser or radiator
soiled.
- Activation of Coolant Fan -
V7- (step 2) from A/C
Pressure Switch -F129-
malfunctioning.
- A/C Pressure Switch-F129-
faulty
- Malfunction in A/C coolant
circuit (positive or negative
pressure).
- Locate and repair open circuit
using wiring diagram:
- Check activation of Coolant Fan -
V7- (step 1) output Diagnostic
Test Mode Page 01-79 and
electrical testing Page 01-253 .
- Clean condenser and radiator.
- Check activation of Coolant fan -
V7- (step 2 via A/C pressure switch
-F129-) ( Page 87-57 ).
- Check A/C pressure switch -
F129- ( Page 87-57 ).
- Transfer vehicle to an Audi dealer
which is authorized to carry out air
conditioning repairs.
- Check pressure in refrigerant
circuit
Page Diagnostic Trouble Code (DTC) table e 20 of 56
http://127.0.0.1:8080/audi/ser...A01.0... 7/19/2005
01-43
Notes:
This malfunction only applies to vehicles up to model year 2001. From model year 2002 High
Pressure Sensor G65 is installed instead of A/C Pressure Switch -F129-.
Electrical Wiring Diagrams, Troubleshooting & Component Locations
The A/C Pressure Switch -F129- consists of 2 switch elements:
The compressor is deactivated via terminal 1 and 2 if the pressure in the refrigerant circuit is to high or
too low (switch opens).
The coolant fan is switched to second speed via terminals 3 and 4 (switch closes).
If the switch between 1 and 2 in A/C pressure switch -F129- opens, the A/C Control Head -E87-
initially assumes there is excess pressure in the refrigerant circuit and stores this condition as a
malfunction. If the measured ambient temperature is between 0 c and 50 c and the switch remains
open for longer than 30 seconds, the system switches from excess pressure to low pressure (low
pressure switch function) Read measuring value block Page 01-134 (Display group 01
compressor cut off conditions).
If A/C pressure switch -F129- registers a "high pressure switch open" 30 times during a driving cycle
(e.g. because of a loose connection), the compressor is switched off. The compressor can be
switched on again by pressing the "Compressor on" button, or by switching the ignition off and on
again. If this malfunction occurs over several driving cycles, the compressor cannot be switched on
again unless the DTC memory has been erased.
Page Diagnostic Trouble Code (DTC) table e 21 of 56
http://127.0.0.1:8080/audi/ser...A01.0... 7/19/2005


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## Jettacli (Jan 13, 2005)

*Re: air con not working - 00792 - A/C Pressure Switch (Jettacli)*

fixed - replaced the a/c pressure switch and all is working fine now.


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## nicks_ (Sep 10, 2014)

*Same Error*

I've got the same error code, what pressure switch did you end up purchasing? I'm not sure what i'm looking for honestly.


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