Hi Darryl,

The air conditioner compressor works to keep the cabin cold air box located behind the Glove Box to around 42deg F regardless of what air temperature setting you have in the car.

The Hot/Cold air system work like this;

There are 2 air boxes behind the dash. One air box is for Hot air and the other Air Box is for Cold air. The Hot air box is maintained at Engine temperature (around 192deg F). The Cold air box is maintained to a temperature around 42degF. The cabin fan blows air through the air boxes to the setting you set on the dashboard dial. That is if you set the setting on the dash dial to Red air will be blown only through the Hot air box. And if you set the dash dial to Blue then the air is only blown through the cold air box. Any setting in between Red and Blue will blow air through both boxes so that the desired air temperature is reached in the cabin air vent.

The cold air box on some cars have a shut off. That is if the outside air temperature falls below 42degF then the air compressor will not turn on. I am not sure if Volvo added this feature to their cars. And the Hot air box is always hot regardless of out side temperature. Some car manufactures have a shut off valve to control the hot air box. So when you need hot air engine coolant will be allowed to circulate through the heater core. Volvo keeps the hot air box hot all the time.

Hope this helped,

Steven---