2007 A3 8P A/C issue

[ramack]

My daughter's 2007 A3 air conditioner hasn't worked well since she bought it. I'm expecting it to be the pressure switch(G65) or the solenoid valve (N280). It appears that the G65 is probably more common than the valve, but don't want to shotgun the problem. I did come across a video and the guy made a comment that the valve can be R&R'd without having to evacuate and recharge the system? Is that correct?

However, the solenoid valve will discharge the system?
Thanks,

[ramack]

This is the weekend for AC work. I repaired the AC in our 2010 Honda CRV, new compressor, flushed the system and got everything back together. Best it's been since we've owned it.

I do not have VCDS, so I don't know any of the live data values, but no codes are being thrown. I have taken pressure reading before, but I can't find them, so I'd be guessing at any values to post. Previous owner had made comments about the AC acting "weird". I'm guessing he had done some work, but I don't trust his abilities. I don't think the pressure measurements were all that great, but as mentioned I can't find what they had been. While I had the tools out, I evac'd the system, pulled a vacuum for a couple hours, then refilled with ~18oz of r134. The ECON light stayed on, but went off after I restarted the car.

Pressure readings are:
Low side: 50-55psi
High side: 145-155psi
Ambient temp: 90F

Based on the Honda's readings which has a similar capacity of oil and refrigerant, the high side is about 125psi low. I can hear the compressor cycle as I toggle the AC on-off, so the solenoid valve is functioning, but since I don't have the VCDS, I don't know what the high pressure is or the duty cycle.

[ramack]

I'm working on borrowing a VCDS to use and dig out the measurement block. Called a couple of Audi shops(non-dealer) for some info. $200 just to put eyes on the system. I can buy a 3 VIN dongle for that much, so I'll try to do as much as possible.

I've double checked the refrigerant charge level a few minutes ago. Pretty much at nominal for static pressure readings. It's 91F and gauge pressure is showing ~100psi. Nominal static pressure is 104psi, so I've got the correct charge amount. That's another check box marked...

[ramack]

I'm needing some guidance on diagnosing the AC issue with this vehicle please. No HVAC codes are being thrown. I've been able to get access to the VCDS dongle and have installed the software. From multiple forums, including Ross-Tech's, I've checked the high pressure switch (G65) and evaporator temperature sensor (G263) sensors and they both seem to be functioning properly (based on my limited understanding of this system). Suggestions from Ross-Tech point to replacing the G263. VaG's inventory system was down last week, the closest stock was Texas and soonest arrival was Monday or Tuesday. I found another source and that part is to arrive today (Sunday). However after a few tests yesterday, I don't think that the G263 is the issue.

With VCDS connected to the vehicle, I removed the sensor from the evaporator box. Still connected to the wire harness, with a small bag of ice I cooled the probe down to 0C and watched the response. Then I removed the ice and let it return back to ambient temperature. Watching and logging the response, it appears to be functioning correctly. So I'm not expecting the new G263 to have an effect.

The high pressure switch seems to be another common sensor to fail, but it to appears to be functioning properly. The pulse width duty cycle seems to match the response in the AC manual, so I don't believe that's the issue either. The N280 solenoid is working in terms of it's cycling on and off when commanded. But I'm confused why the duty cycle doesn't go higher. The high side pressure has never gone above 125-150psi, and as a result the vent outlet temps have never gone below 60F. Even when the ambient temp is 70-75 in the morning.

I'm beginning to wonder if it's something with the climate control module, and it's not commanding the N280 correctly. Are there settings in that module that I can check to see if those are set correctly?