# location of aircon pressure switch (f129) ?



## jhoneyman (Aug 8, 2012)

Had my aircon gassed and found the compressor doesn't kick in. I have this fault code : 00792 , which points to the f129 (ac pressure switch )

Question is where is the damn thing located ?
I have done some digging here but it isn't located where expected.

I do have a 2000 APX model which I think must make a difference.

Any thoughts ?


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## Hoggy (May 8, 2002)

Hi, Top left hand corner of engine bay. Can be removed without loosing pressure, always replace "O" ring.
From 2001 onwards known as G65 but same position.
Hoggy.


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## DTH (Sep 24, 2015)

Serendipidy

Just had my 2002 225 MOT'd today (Passed - flying colours BTW  ) While I was there I asked if they could have a look at my aircon as it's not worked since I got it - the system is pressurised and all fuses are ok. Now the chap has said it could be the pressure sensor as its showing no pressure in VAG but the system is full. After reading the reply from Hoggy I've just been out for a look-see and cant find it - does anybody have a piccy of the location I should be looking for it? Seems like a cheap / easy thing to try?

Many thanks chaps!

Its a 2002 225 (BAM) BTW [smiley=book2.gif]


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## Hoggy (May 8, 2002)

Hi According to Bentley but will check mine tomorrow.








Hoggy.


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## DTH (Sep 24, 2015)

Faaaantastic! Thanks for the piccy, Much appreciated. 

Right - off to the car - wheres my torch?!


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## jhoneyman (Aug 8, 2012)

Sadly it's not located there on the APX.
It must be somewhere out of view.


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## DTH (Sep 24, 2015)

I cant find it on mine either?!


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## jhoneyman (Aug 8, 2012)

DTH said:


> I cant find it on mine either?!


And yours is a BAM, so different from mines slightly. 
I reckon it is behind the strut brace and into the firewall on the passenger side of the engine (near the brake fluid) 
I'm heading in there tomorrow morning :roll:


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## jhoneyman (Aug 8, 2012)

Managed to locate the Pressure switch.
it is certainly hidden on my model of car/engine. (2000 225 APX)

You have to remove the strut brace and the boost pipe as well as folding back the aluminum heat shielding and then remove another heat shield which surrounds the switch (pinned with 3 pins)

Here we are for reference purposes:


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## jhoneyman (Aug 8, 2012)

Now that I have located it and all seems fine wire/connection wise I now want to order the part.
There are two part numbers listed for this part.

1H0959139 (termed high-low pressure/fan switch) which covers chassis' up-to 8NY 065480

&

1J0959126 (termed thrust sensor) which covers chassis' from 8NY 065 481

Now my chassis number is TRUZZZ8NZY1076511 which looks like I require the later part number being 1J0959126 .

in comparing the two switches (Google search) The one on my car actually looks more like the first part number.

Any thoughts on this matter ?
I had a similar issue with power steering pipes off late and ended up fitting the "wrong" pipe which turned out to be the correct one, so my car is a mixture of new and older parts it seems. It was manufactured at a crossover period so ETKA is not entirely accurate at times with my car.


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## jhoneyman (Aug 8, 2012)

To end this thread My aircon is now working again.

I let eurocar parts find the correct part for my car.

So hopefully if someone searches on this issue in the future this thread will help you locate the "phantom" sensor location etc..


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## DTH (Sep 24, 2015)

Excellent stuff! Chuffed it's sorted, hopefully I'll have the same result when I get one ordered.


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## DTH (Sep 24, 2015)

Hi,

Still not sure what to order, when you got it - did it look like this? 
http://www.ebay.co.uk/itm/AUDI-A3-TT-PR ... SwQItT42JN

Or this...?

http://www.ebay.co.uk/itm/Air-condition ... Swj0NUcgMp

Cheers!


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## jhoneyman (Aug 8, 2012)

DTH said:


> Hi,
> 
> Still not sure what to order, when you got it - did it look like this?
> http://www.ebay.co.uk/itm/AUDI-A3-TT-PR ... SwQItT42JN
> ...


This is an easy one..

They way I determined the correct part in the end was by the connector.

One is oval with 3 pins and one is square with 4 pins.
Just check the connector on your car and you are golden.

I bought the oval connector for my car.

Just to recap and from the links:-

1H0959139 (termed high-low pressure/fan switch) which covers chassis' up-to 8NY 065480 (Square connector - 4 pins)
http://www.ebay.co.uk/itm/AUDI-A3-TT-PR ... SwQItT42JN

&

1J0959126 (termed thrust sensor) which covers chassis' from 8NY 065 481(Oval Connector - 3 pins)
http://www.ebay.co.uk/itm/Air-condition ... Swj0NUcgMp


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## DTH (Sep 24, 2015)

Hi,

Im at the sensor now - its not shifting and I'm worried about damaging the connected pipework if I apply to much pressure - looks like Aluminium - did you struggle to get it off?

Cheers


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## jhoneyman (Aug 8, 2012)

DTH said:


> Hi,
> 
> Im at the sensor now - its not shifting and I'm worried about damaging the connected pipework if I apply to much pressure - looks like Aluminium - did you struggle to get it off?
> 
> Cheers


It was tight on the pipe yes. More leverage using a longer spanner helped break the torque


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## DTH (Sep 24, 2015)

Cheers, managed to remove and replace it - still no aircon  
Anyone know a good aircon diagnostic guy in the NW?

System is pressurised and there is a significant enging speed change when pressing Econ. No fans kick in at all though :?


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## jhoneyman (Aug 8, 2012)

DTH said:


> Cheers, managed to remove and replace it - still no aircon
> Anyone know a good aircon diagnostic guy in the NW?
> 
> System is pressurised and there is a significant enging speed change when pressing Econ. No fans kick in at all though :?


This actually happened to me once I had replaced the sensor.
The fans wouldn't come on... I ran the car and had the aircon on.. I then removed fuse 16 and the aircon one in the engine bay and then replaced them. Fans kicked in and aircon fine now


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## DTH (Sep 24, 2015)

jhoneyman said:


> .... and the aircon one in the engine bay and then replaced them. Fans kicked in and aircon fine now


One of the three on top of the battery?

Which one was it?

Cheers

Dave


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## jhoneyman (Aug 8, 2012)

Yes.. as below:-


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## DTH (Sep 24, 2015)

Thanks for getting back to me  
But still No Joy :? 
Guess I should try swapping out the fan control module next.


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## DTH (Sep 24, 2015)

Fixed it!  
Took everything out to get to the FCM - found that one of the thick wires from the large 4 pin plug coming from the Fan Controller Module had worn away on the underside of the battery mount, water had got into the wire and it had turned to magic blue dust.

One swift chop, trim, clean, solder, shrinkwrap and reassembly is the reverse of removal later....

Ta Daaa! - Air con so cold it's painful 

Took lots of piccys - would be a good thing to write-up for when other peeps have the same issue.
Do I need an external photo host or can I upload to the site?


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## Hoggy (May 8, 2002)

DTH said:


> Took lots of piccys - would be a good thing to write-up for when other peeps have the same issue.
> Do I need an external photo host or can I upload to the site?


Hi, Just use "upload attachment" in each reply....Upload from your PC... Phone/Tablet may not be so easy.
Hoggy


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## DTH (Sep 24, 2015)

Thanks Hoggy - never noticed that!
Picture below shows the corroded / disintegrated wire.
This generated no codes at all....


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