There is no belt-squealing noise so it can not be a slipping belt.

Have you checked the fluid level.(power steering)

there`s a chip on the steering column you might want to get that checked out it helps control steering..

It could be the power steering pump itself going bad. That would be my first suspect. Check the website below for many Volvo experts. They can probably give you some things to look for.

Steering pump bypass valve sticking.Get a scrapper pump

there r 2 possibilities for this
1. if rack has no assist when car is first started [generally first start of day] but assist comes back after car warms up. the seals in the spool valve r shot [bypassing fluid internally] & replacement of the rack will be required
note:[low buck re-manufactured no- name racks r subject to be as bad as the one u just took out]
2 less often the steering pump fails. this can be determined by momentarily pinching shut the pressure hose with engine at idle.
if bypass valve is stuck open there will be no change in engine speed.
if working properly the engine will bog down & constant idle motor will open to a larger setting as computer tries to compensate idle speed.due to the increased load