I had different symptons when my (I think it was capacitor) went - blower only worked on 4/high, lower 3 speeds didn't work. Sorry, don't have part numbers or anything. The one for climate control had some about 2" fins that protruded into the blower/heater housing. You need to pull the glove box and the panel underneath. Capacitor was right in the center of the white plastic housing, 3 or 4 screws and it's out.

Cost with climate control was about $100, without about $70. That was through a local Volvo parts place, you could likely find them cheaper. Not sure from the symptoms you have if that's the problem or not, but sounds like a likely suspect.

Good luck,
Scott