Really depends on the model.

The common fault with this unit is the white marshmallow looking thing where the harness connectes with the plate. There is a tiny gap between the white thing and the plate, and the metal connector is subsequently exposed. Over time that connector can rot off the plate. There is no fix for this problem save for buying a new sender (which comes with the harness permanently attached to the plate).

Other problem sources include the pre-pump fuel line on the sender (a hoseabout 3" long), and the contact where the tank level monitoring arm rubs against the sendernozel arm. It's a little elctrical contact, and the position of the arms against each is what triggers the tank level.

The hose canbe replaced, but the contact is really unfixable.

Basically if you are having problems with your sender just suck it up and buy a new one, buy a used one, or deal with it if the only problem is the gas level. It's not a piece that's made to be fixed. The part will cost you $352 from Volvo, but you can find it online for $270. If you want to save some cash get a used one from a junker for a lot less.

good luck,
rt