There have been problems with the climate control system not working at times. Volvo has made a Software upgrade for the AC control module is available that can correct certain climate control system faults.Google+
Car Problem Reports
Volvo XC90 Software Upgrades Will Fix Climate Control System Problems
Volvo XC90 Problem
Average Mileage: 106,256 mi (72,567 mi - 217,000 mi)
Visitor, 2004 Volvo XC90, 124,000 mi
fan speed button on the climate control stopped working
Visitor, 2004 Volvo XC90, 80,000 mi
blower motor stop working
Visitor, 2006 Volvo XC90, 98,000 mi
Fan stays on all time
Visitor, 2007 Volvo XC90, 80,000 mi
Ac stops at times and comes back randomly
Visitor, 2004 Volvo XC90, 91,000 mi
After driving 2 hours on highway in very hot day 100+ F.
Blower speed control stop working. Blower start working in two stages off or full speed.
During couple hours stop, after ignition off, blower did not stop and was working all time (2 hours).
While next 1 hour drive temperature control stop working. Was stuck on cold. AC on/off button was working.
Visitor, 2006 Volvo XC90, 217,000 mi
have had same trouble with fan speed control not responding or changing force of blower on its own - told I need new climate control module and software upgrade for approximately $1800 in part(s) and labor. Haven't done it yet as I as trying to find out if way of getting software upgrade without replacing climate control module to see if that fixes it (if you can even get such an upgrade without getting a new part/module??).
Visitor, 2005 Volvo XC90, 72,567 mi
the climate control fan, i can not stop.