To check the air pump, lay down under the battery area and unplug the pump from the relay. You're looking for the connector with the blue wire as there are three plug ins to that relay if I remember. Take a jumper wire and put 12v on the pumps blue wire. If it runs, the pump is good. Your problem is then (1) THE RELAY (2) THE SAS valve or (3) the small selonoid located on the inside lip of the fan shroud with the purple and white vacuum lines running to it. The blower is the most $$$$$ of the 4 parts. Groton gets near $300. with the dealer getting $400.+ depending on how many more of his customers he wants to screw that week. I found a new pump on ebay for $150. but they're scarce. Check down the list of posts here. There is a fairly simple way to convert a VW pump to work on volvos and they're cheap like < $50.