Blowing hot air. It has never been super cold since I got it a year ago. But this summer is totally dead. I attempted to refill it with the auto parts freon, DIY with zero effect.
What is the most likely cause of failure? Compressor? How expensive will it be?
about 200K on it, but the engine has 50K on it FWIW.
No telling without proper diagnostic tools. Could be a bad switch or leak or the compressor or all of the above.
If you are determined to get after this yourself, you need a bi-directional scan tool to pull up the internal codes for the AC system.
You'll also need a proper manifold to check hi and lo pressures and to introduce refrigerant into the system properly. A vacuum pump and leak detector should be on the list as well.
Use GM parts, I've had even aftermarket gaskets and schrader valves fail right away on me.
If yours were mine I'd first check for codes related to the system and then discharge the system and see if there's a leak with the vacuum pump/manifold and take it from there.