2015 Jetta A/C problems

I have a 15 Jetta TDI. When you start the car the AC works no problem, but eventually it will blow warm air instead of cold. If I push the AC button off and on it will eventually come back and work fine. I talked to one shop and he wanted to replace the compressor. Is this a compressor issue or something else?

AC cannot blow warm air. So if there is heated air coming through the vents then something is causing the temp blend door to command the air be pushed over the heater core.

So...is the AC maybe just not cooling?

ah, yea you can diagnose your own stuff and do ALL the work yourself for about $450 with all the tools. thats compressor, refrigerant, vac, gauges, the works.
You can start with about $10 and find our why its not running
After going though the electrical stuff, and you think its the compressor, use a strip gauge oil tester to test the PAG oil for acid from burning. And a set of gauges to read the pressures. But thats AFTER you work on the electrical.
this could simply be a $20 part you can DIY yourself
First step is to see if the ambient air temp switch and the high/low pressure switch AND most probably the fan control is all working fine. you can jump them, look up the write up on it, simple and supper easy to do.
99.9% chance your charge and compressor are FINE
when compressors fail, they do not behave like this.
85-90% of ALL HVAC car or building issues are electrical.
Chances are that the fan is not coming on for some reason and the system shuts down to protect from too high pressures.
Start with a volt meter and a piece of wire. im not big on the 2015's or most of the newer cars but the principle is the same across the board on most cars. Jump the pins on the pressure switch and the fans should come on, Test the ohms on the ambient air temp sensor and so forth. Do a search here on the write up for your car.
Best of luck. and dont go back to that ripoff who wants to work on the system.
in the HVAC world, if you ever have a service and the tech starts with his set of gauges, FIRE HIS BUT off the job site.

Mongler, please stop trying to give advice on cars you do not know anything about. You are not helping.

That car has a completely solid state electronic (not "electric") HVAC control system. There is no "jumping" things, you can fry control units like that. The scan tool is the first item to grab when diagnosing a system like this. Chances are the RCV is to blame (there is a TSB about this, it is very common), but this is assuming that the system's cooling is not up to par, and not a temp control actuator or interior temp sensor problem. Again, AC systems cannot blow hot air. They can cool the air, or not cool the air, they cannot heat it up.

fine, but you can still test the sensors right? i dont think we have transcended past being able to measure the real world yet!

Verification of the inputs can all be done via a proper scan tool, and what the controller is seeing is ultimately what is important.

In the case of a refrigerant pressure sensor, you are dealing with a 3-wire affair, low reference voltage, and variable feedback. It is not a "switch" that is ON/OFF. The RCV on the compressor is duty cycled, depending on demand and load. The fans are controlled again by a data signal to the left cooling fan motor, low voltage signals, that in turn is requested by the Climatronic/Climatic HVAC controller.

Jumping things and Ohm checking things just isn't the way we go about diagnosing things like this anymore. It is far more complex, but it is all made fairly easy via the scan tool capabilities and are ability to utilize not only the onboard fault gathering but data displays as well as in many cases some basic input/output tests. All without getting your hands dirty, all without even opening the hood.

good to know. glad to avoid.