Heater core / coolant question
 

In order to drain the coolant from my '95 850's heater core (when doing a coolant change) do I have to have the heat on with the temperature set to hot like on older vehicles or is the heater core pressurized all of the time with the rest of the cooling system and it will drain out regardless of the heater setting? And I am doing the draining from the back of the block and the bottom of the radiator. Thanks.

The only reason you'd need to have the heater control on "hot" is if the vehicle had a heater control valve in one of the heater hose lines. The Volvo uses blend doors to modify or control temperature so there is no valve.