AC VCDS codes

I was able to borrow a VCDS last night to scan my car and hopefully determine why my AC isn't working. Here are the faults I got that were AC related:

Engine-
Please check DTC memory of AC controller
P1641

Auto HVAC-
High pressure sensor (G65)
009 - open or short to ground
Refrigerant pressure
002 - lower limit exceeded (note: I checked this a few weeks ago and the pressure was high on the gauge using AC recharge bottle from Advance Auto)

Instruments-
Outside air temp sensor (G17)
010 - open or short to plus - Intermittent


Anyone have any suggestions on where to start? what to check? how to check it?

Been seeing a lot of the A5's left fan (the one with the controller integral) going bad causing inoperable fans. But your A/C should still work, albeit poorly and not much at all if you are not moving.

You may have a bad pressure sensor, and that may have failed because one or both of the fans are not working properly.

There is also some issues with the pressure duty cycle valve on the back of the compressor (these compressors have no clutch) that can cause overly high pressures and damage things. Volkswagen (Sanden) has an updated compressor for this.

Is the high pressure sensor (G65) mentioned in my first post the same as the bad pressure sensor that you mentioned? From what I've read I assume it is and it's located on the bottom of the radiator?

The G65 is the high pressure sensor installed in the end of the line fitting at the condenser. They may be in a slightly different place as some of this stuff changed on 2005.5 cars versus 2006.

There is a TSB I have here about HVAC DTCs 00819 and 00229 but the solution is "still pending" whatever that means (but Alldata is always behind). 8708-04 is the TSB number I have.

...still looking....

OK, further TSB info says check G65 for leaks or wiring connector issues, and replace with part number 1K0-959-126-A if it is leaking.

Another picture I have show it very near the front of the compressor, towards the condenser. But I am almost certain not every A5 has the G65 in the exact same spot.

Hope this helps.

Did the codes clear? If so did they come back in very soon?

I would look at wiring issues. Either one of those sensors, or the wiring to them, can prevent operation of the AC system.

While you have the VCDS do the ENGINE OUTPUT TEST this tests the ECU's ability to run the fans and is independent of those sensors.

It would not be unusual for either of those sensors to fail, but the two at the same time would have me look hard at the wiring. Rodents, fretting from vibration.

Thanks guys I'll try some things this weekend. I don't have the VCDS still but might be able to borrow it again

Trying to tackle this today.

So far:

Haven't found any wires that look bad or even close
Confirmed that I have 12V going to the fans
I don't have any power going into the sensor that is on the bottom passenger side of the radiator or whatever sensor is on the back of the compressor

Anyone have anything to check next?