AC System not working 1.2 12V 2005 9N

[vargabp]

Hi!

Recently bought a 2005 1.2 12V Polo. AC was not working at the time of purchase, and went to re-gas it at the local Kwik Fit to try and fix the issue, but the AC would not kick in even after that. I could not leave the car there unfortunately; I needed to be on my way urgently.

It seems to be a clutch-less compressor so it is constantly being run by the belt.

I managed to find some time to connect it to VCDS and the refrigerant pressure read 0 bars. I'm thinking that if the sensor were not faulty and the system leaked, it'd still show at least 1 bar (normal atmospheric pressure). This is the error message:

Control Module Part Number: 6Q0 820 045
Component and/or Version: Klimaanlage X0840
Software Coding:
Work Shop Code:
2 Faults Found:
00819 - High Pressure Sensor (G65)
07-00 - Signal too Low
00898 - Control Circuit A/C compressor
30-00 - Open or Short to B+ - Intermittent

After a bit of research, and excluding refrigerant pressure (due to just having it professionally topped up) it seems that the wiring leading to G65 or the actual G65 or both could be faulty.
The second code looks more severe and it could be any number of things (including compressor failure), so I'm trying to separate tasks into small chunks, and try the cheaper fixes first.

1. Can someone help me locate the high pressure sensor to try and measure it's output?
2. Can the sensor be replaced without having to re-gas the system? (if the sensor has a pin that pushes a valve in to have access to the pressure inside the system)
3. Can the sensor be bypassed? The signal that it is supposed to put out must trigger something else, that can be activated for testing purposes.
4. Where do I find diagrams or schematics for this specific model? My time on google has not been very fruitful.

Thank you!

[RUM4MO]

I've forgotten on that version of Polo where the pressure sensor is, but typically it will be on the high pressure pipework and located maybe on the RHS of the engine bay, follow the smaller diameter alloy pipe and you should find a sensor screwed into that pipe.

I would not think that you would be able to make much sense out of any raw data or signal coming out of that sensor, maybe check that there is power getting to the controller, though VCDS would not be able to communicate with it unless it was receiving its 12 power supply and earth.

These pressure sensors are well known to cause trouble by failing and/or leaking, if it is leaking there will be a build up of oil mist around that sensor, buying aftermarket replacements is normally a bad idea as if VW Group's main supplier can not make ones that work for too long, why would you expect an aftermarket supplier to provide as good or even better.

The compressor control signal issue is probably a wiring failure.

[vargabp]

Thanks for the tip, I'll have another look tomorrow morning.

Is there any way of overriding the sensor? If AC were to start after jumping the sensor, that would indicate that it is clearly faulty.
LE: Yes, the sensor can be bypassed with this method watch?v=0vhNkgJqRZo

Can't wait to find the little bugger.