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).
2006 XC70 White only 59,000 miles. New daily driver.
2000 V70R Silver, 36,200 miles!!! SOLD (I will regret this)!
Contact info for purchases: jrl1194 (at) aol (dot) com