My wife's A/C works sometimes, when I say this I mean it will blow warm air for some time then it will start blowing cold. This will switch back and forth the whole time driving. There is no set amount of time for each cycle. I have changed out the compressor, ambient air sensor and we had an A/C shop change the dash unit. Nothing has helped yet. The local dealership can't figure it out, the local A/C shop can't figure it out and neither can we. The one thing I notice is when it blows cold the recirculation light is on on the dash unit. It will switch to bringing in air from the outside and then it will stop blowing cold. I am guessing it is something in the computer but no one can figure it out. Any ideas or advice is greatly appreciated.

Hi
I know this might sound stupid, but did you fill the A/C compressor with gas after you changed it? Also, recently one of my family vehicles had a problem where the A/C would not really cool the car much at all. This is on a 2005 Lexus RX330. Originally, my dad thought that it was the radiator fan control mounted in the top middle of the radiator fan assembly. When that didn't work, he changed the entire radiator fan assembly with a brand new one. Now the A/C blows ice cold air all the time. It could potentially be something wrong with the ecu/computer, but I'm not very knowledgeable on that.
Those are my suggestions, I hope they help