Help me find the correct AC clutch

[Jmac]

Sounds like only thing missing here is to have a VW tech look at it. Pm sent
Jmac

[Shadow_Rusty]

Been looking through the circuit diagrams, and everything leads back to the "Control Unit For Radiator Fan"

Looks like this is the central point for Fans / Water Pump / Aircon Compressor...
Still looking further, as I'm in a similar boat to you...

[Update]

Looks like there are 4 main parts... (With most likely cause being 2/3)
1. Climatronic (About a billion wires and connections going everywhere...)
2. F129 - Air Con Pressure Switch
3. F163 - Air Con Shut Off Thermo Switch
4. J293 - Control Unit For Radiator Fan


J293 (Control Unit For Radiator Fan) (T10B)
Pin 2 - Input from F129 Pin 3 and climatronic
Pin 5/8 - Input from F163 Pin 2
Pin 6 - Compressor Ground (Shared with thermo fans)
Pin 10 - Compressor Activate

F163 (Air Con Shut Off Thermo Switch) (Should be Closed Circuit To Enable the AirCon)
Pin 1 - F129 Pin 1
Pin 2 - J293 Pin 5/8

F129 (Air Con Pressure Switch)
Pin 1 - Climatronic Control J255 (T16B / Pin 2) and F163 (Pin 1)
Pin 2 - Climatronic Control J255 (T12 / Pin 2)
Pin 3 - Climatronic Control J255 (T16B / Pin 10) and J293 (Pin 2)
Pin 4 - A20 Conection (15a) in dash panel wiring harness (Assuming fuse box, but not sure)

[JustCruisn]

I don't have the F129 - I have G65 3 pin variable signal pressure sensor. It sends a duty cycle value to the J293 Fan control unit. under 20% is low pressure cut out, 90% is high pressure cut out.
Also pin 3 on the J293 Fan control box (T14/3) is not used, it is plugged on the connector.
The G65 runs to pin 2 (T14/2) white line, on the fan control unit.

There is a fault logged for this sensor. I've replaced the sensor and the control box and the fault keeps coming back.
An auto sparky diagnosed that the signal line from G65 was going to ground in the J293 Fan control unit. I'm suspecting it is still going to ground but not in the J293 fan control unit but rather in the harness. The line also goes to the J220 Engine control module, maybe it is grounded on its way there.
I'm going to try to diagnose it further this weekend. I'll have to test the sensor directly without the harness connected to see what is actually coming out of the thing.

---------- Post added at 08:21 AM ---------- Previous post was at 07:43 AM ----------

I'll have a look at that F163 cut out switch too, that sounds like a good hunt.

Here are some resources I've found helpful.

Good discussion
AC doesn't work - Page 3 - TDIClub Forums

Fan control module pinout
http://pics.tdiclub.com/data/529/J29...rol_module.pdf

Guide to diagnosing the Fan control module
Fault diagnosis in the Fan Control Module - Gtivr6wiki

---------- Post added at 04:08 PM ---------- Previous post was at 08:21 AM ----------

UPDATE - SOLVED

I tried a few more things today and got nowhere. Then I decided to try the old pressure sensor I'd replaced. Turns out the old one was not faulty at all, this was suspected after finding the fan control unit fried and grounding the pressure signal.
The new one was the dud, I had trouble believing that, its always possible that the a replacement part it faulty but is a hard thing to believe.

Thanks to everyone who took time to help me with this. Especially Gavin (h100vw) who drove all the way out to Kenmore for me.

[Jmac]

Good result, i remember calling the pressure switch early in the piece when you called me at the airport, what a bummer the new one was a dud, does make it hard when the new one should be good, see that heaps with air mass meters and can really waste time, thinking you have nailed the bad parts, and then keep looking to find yourself back at the bloody thing.
Result is the main thing
Jmac

[h100vw]

You're dead right Jimmy, calling time on an already replaced part is hard but as you have said sometimes you have to stop and start over again. It makes more sense, when you stop trying to figure the new part in the troubleshooting.

No worries on the trip for me Chris, I got some precious beer! Lucky you got it fixed with all the hot, dry weather we are having?

Gavin

[Jmac]

You're dead right Jimmy, calling time on an already replaced part is hard but as you have said sometimes you have to stop and start over again. It makes more sense, when you stop trying to figure the new part in the troubleshooting.

No worries on the trip for me Chris, I got some precious beer! Lucky you got it fixed with all the hot, dry weather we are having?

Gavin

Hmm Beer, wish i had been there with ya now Gav LOL.
Maybe should have sent my Doppelganger hey, never been so snowed!!!
Any result was had thats the main thing
Ill be looking for a Doppelganger in the New Year i think but you need to have sidees to pass the interview
Cheers
Jmac