Older Volvo's have cable controlled temperature. Not sure what the cutoff date is. If you're hot/cold control is a lever you slide side to side, then follow the cable. It's either broke, disconnected or the water valve is stuck. A clogged cabin air filter will prevent air flow only when the fresh air is in the vent position. In the recirculation position, it by passes the cabin air filter and you'll have full air flow.