Where is the ac Refrigerant circuit pressure read from

[Bamared]

Earlier today I was reading my OBDeleven live data for ac. My circuit pressure was 1bar, than I held down the eco button, and the ac started working at than was reading 8 bar.
Thinking I have a bad sensor, I shit off the engine and restarted and now it’s reading 33bar. Normal operating says 2.5 to 29.

Since it at 33 bar, the ac won’t start again as it thinks it’s over pressure.
G65 high pressure sensor continually reads 0.0, when it’s working or not.

[Audibot]

The pressure switch is located on the driver's side of the condenser, right by/next to/below the headlight. You can see it in the gap there. To remove/replace it, I think you are supposed to pull the bumper off.

Note the switch reads the high side before it goes into the condenser, and is required to have a reading (non-zero) to turn on the compressor. I'd start by replacing that switch. Note that if it's dirty/oily there, the o-ring is bad and it's been leaking. But I doubt it's leaking because it's holding 33 bars.

The pressure you are seeing at 33 bar is the low side, but in your case, it's the system pressure throughout, since the compressor is not turning on. I have experienced both a leaky switch (leaked past o-ring) and a bad compressor.

[Bamared]

Yup, that is the switch I checked today. I just pulled the headlight off and got to the switch pretty easy.
What I found was, it was loose. So I took it off and when I disconnected the connector it still was reading 33 bar on OBDeleven. I connected it while it was off the condenser and it still reads 33 bar.
I bought what I thought was the correct new sensor, but it wouldn’t thread on, and had a deep bore than threads... and the o ring it came with was to big. But when I connected that one sensor to the wires, OBDeleven was reading 1bar.

I think, if the sensor is disconnected or bad, the system will read 33 bar, as the limits are 2.5-29 bar to operate.

Now I’m wondering why the sensor I ordered was not correct, I’ll do some more research to see wtf part number I need.

[Bamared]

So I checked the pressure Sensor, they sell a long on with a hex looking shaft on it, which was way to long and deep to thread on. The original is much shorter, so I ordered an original and will see what happens when it arrives.

The saga continues!

[Bamared]

Installed the g65 pressure switch today original from Audi and seems to be reading pressure correctly.
Old switch installed was not original and a tan color, which i think failed internally.

I been warned to not focus on pressure washing much in that area, just Incase.

Symptoms I was having-
Eco light on and wouldn’t reset
Eco light randomly turn off and ac work
OBDeleven reading live, 001, pressure 2bar,1 bar, 33bar.... sometimes 3-4 bar when working ac.
OBDeleven live, 002, compressor on and off “ low pressure” high pressure”, intermittent.
Faults,
Pressure signal to low
Pressure signal to high
Intermittent
Static g65

[Theiceman]

So what exactly are you saying ? Is it fixed or not ?

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[Bamared]

Yes it’s working,

[jasc23]

I am experiencing the same issues.
And yes, if your scanner (VCDS, OBD, AUtel, etc..) are reading 33bar, it DOES NOT MEAN that your pressure in the system is 33bar. That would be crazy as 33bar is like 500PSI and at that point one of the lines would for sure explode.
Some here keep saying that if your pressure is 33bar, your pressure is too high and you need to bring it to have the system checked.
33bar simply means the sensor is open or not sending the correct signal. I have also tested 3 different sensors at this point: 2 MAHLE units (Confirmed they don't work) and 1 Chinese crap (EVEN WORSE).
I too ordered my sensor from EROPA PARTS and really crossing my fingers it solves the issues of the A/C reading 33bar when the engine is running, but when running on 12V (alternator disconnected), works perfect.

[Theiceman]

that sensor gives all the input to the control module so it can make correct decisions ( system pressure to low will not start compressor, system pressure too high will shut down compressor etc). all these conditions will cause eco light to go on . which essentially means A/c is off.

always start with gauges, (verify with external test equipment ).
then go after that switch with an OE replacement ( original equipment ) .

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