It probably IS your compressor.
What is happening is the compressor clutch is weak and when it becomes hot it can't 'hold'
Search the site, there's a DYI quickie clutch gap repair that takes about 10 minutes and will work if that's the problem. What you're going to do is shim the clutch out so it can "grab"
When you ask these questions, MILEAGE is important
2000 V70R Black, 121,000 miles (Wife's)
2000 V70R Silver, 36,200 miles!!! SOLD (I will regret this)!
2007 XC70 White, 122,000 miles, loaded and mint, mint, mint in all aspects,
Contact info for purchases: jrl1194 (at) aol (dot) com