Alrighty boys, it's mid june, which means it's time for AC questions.

Two weeks ago, as I was cruising down the highway in phoenix, the AC went from blowing nice and cold to ambient temp for about 20 minutes. I assumed it was an EATC issue, and left it for the time being.

Yesterday, on my way from San Diego to Phoenix, the AC died in Blythe CA. I assumed it was the EATC acting up, so I removed it from its slot, removed the glovebox, and verified that all the vacuum actuators and the blend door actuator works (they do). I also topped up the R-134A, it took about 3 seconds until it was at the correct low side running pressure of 55psi.

Today, the AC didn't pretend to blow cold, and when I got on the freeway there was a buzzing sound and a noticeable lurch each time the compressor engaged. After some more driving, it became apparent that below 1500 rpm, the AC would work normally and it would blow about 60* at the vents, above 1500 rpm it does the buzzing lurching thing and blows at ambient temp.

Am I in for a new compressor/clutch/orifice tube & co., or is there something else I should look at first? Thanks