Hello folks, my ac stopped working one day. Put gauges on and it had static pressure both right at 100psi I was getting 3.5v to the compressor solenoid. I figured maybe the solenoid was not kicking on. I wasn't sure if it needed more as i thought ok maybe doesn't need 12v. I took it to a shop that works on Audi. $300 bucks to look at it thinking they would confirm what I thought. No they come back $3000 for new compressor. They said it was low 1 lbs and that the compressor had failed. My question was how do you put freon in a system that the compressor is not pumping. So I decided to replace the compressor myself. First I removed the freon. I do hvac work on homes so why not. Took the compressor out and looked at the oil clean no metal. So I test the solenoid with 12v and it clicks so now I'm thinking maybe my problem wasn't the compressor. I put the new compressor in as I might as well. Put everything together and no a/c. So I powered the solenoid with 12v and it works really good. But I can't run a jumper wire all the time
so what would cause the solenoid to not get the power it needs to run the compressor. I have looked for the high and low pressure sensors but I haven't located to test. Sorry so long of a story but I live in South Carolina and it's 🔥

 

Of course they tried to sell you on the compressor job...gotta swing for the fences!
An Audi Stealer tech told me A/C compressor was about to fail when had it in for a TDI warranty repair. That was a few years back; still no problems with my A/C other than the crud accumulating right in front of the lower 1/3 of the A/C heat exchanger and engine radiator...right behind the power steering heat exchanger, and effectively reducing/blocking airflow and heat transfer; thereby making the A/C feel weak in car.

If you know A/C, then you can take the static pressure and look up the ambient temp to gauge if the system is low on freon or not. You made it sound like it had been working fine prior, so a pinhole leak is not an uncommon A/C malady if the car has been in Wintry areas using road salt/corrosive chemicals, etc. Pinholes can form right up by the radiator where the A/C pipes bend, and then route into that support structure towards the heat exchanger...that's a very common corrosion spot for the A/C leaking. There's also an A/C sensor mounted right into the heat exchanger beneath the front fascia. Do some research/watch some videos on your issue.

The A/C high pressure sensor is a common platform (aging related) failure point on this Q7. As there are so many sensors/monitored loops on this car, most troubleshooting on the Q7 basically begins with a full diagnostic scan using a VAGCOM type scan tool that can read all the computers/control modules on this car. A/C won't pop a CEL, but there can be myriad sensor fault codes, and/or related codes present if you scan the car via VAGCOM scan tool.

I'd suggest you get a VCDS by Ross-Tech and download/source the repair manual for this car, as there's a lot going on with how Audi's are wired up, and what influences what. What I've learned owning a Q7 is that most of the time it's not the big items that fail, it's the little things like sensors, vacuum line connects, anything made of thermoplastic located on the engine, etc.

There are lots of archival threads on topic of A/C not working, as well as videos on this topic (searched 2014 Audi Q7 A/C compressor not working). Throwing parts at a Q7 generally doesn't fix most issues - you've been warned.

Here's couple useful links:

https://fuseandrelay.com/audi/q7.html

https://www.audiworld.com/forums/q7-...anual-2965007/