It appears that AC problems are fairly common on this forum, but a search didn't produce what I'm looking for.

This is on my girlfriend's car, so I don't know exactly what happened. She was driving home and I guess the AC started to make a funny sound, so she turned it off. Drove a little bit and switched it back on, but now it only blows hot air. The compressor clutch is not engaging when the AC is on. I haven't checked the freon yet. I didn't think that would be the issue since it quit so suddenly. I've been thinking maybe a low pressure switch?

 

First, make a visual inspection of the AC condenser to see if a rock or debris punctured it.

 

You cnn jumper the hi/lo pressure cut-off switch and see if compressor comes on. Stop AC immediately if it engages (cut off AC master switch).
If compressor engages w/ this test, the system pressure is low disabling AC, then a leak is likely.

If compressor still will not run, the an electrical problem is very likely. Possible faults are compressor clutch gap too large, faulty AC compressor relay, damaged wiring.

good luck