Molly,

Re-trace your steps to right before the sluggishness started. Like, did you recently change mechanics or just have a repair done or change gas grades? Do you you have any dashboard lights flashing like SERVICE or CHECK ENGINE? Do a visual check and pop the hood. Do you see anything that appears broken or loose?

Next is to check for error codes. The dealer/mechanic will check the codes as well - and - you'll get charged for it. It's actually very simple once you get the process down. Go to volvospeed.com and choose the maintenance link on the left. Here you'll find helpful knowledge about the more common things that happen to an 850.

I once had sudden power failure/gasping that would occur without notice on my 940T. My air mass meter was dying and causing the incorrect air mixture which would cause sluggishness.

Regarding the AC. If it was working properly before your problem started, then I would think that the climate control is acting as a "protector" so that the car won't crash/overheat since you've got the other problem. Sort-of like a circuit breaker in your home.

Well that's my two-cents.

dpsc