Cooling system (B8444S only)

Fig 1: Compressor (B8444S Only)

Courtesy of VOLVO CARS OF NORTH AMERICA.

The engine control module (ECM) controls the variable A/C compressor. When the A/C switch on the dashboard environment panel is activated, a request is transmitted via the control area network (CAN) to the engine control module (ECM) about the activation of the compressor. The engine control module (ECM) calculates the current to open the valve to control the variable A/C compressor. If any of the following conditions are met, the valve that activates the compressor is not opened:

• high engine coolant temperature (ECT)
• wide open throttle (WOT)
• the engine has just been started
• overpressure in the air conditioning (A/C) system.

When the engine is started the engine control module (ECM) activates the air conditioning compressor for a short period even if the climate control module (CCM) has not transmitted a request for this.

This is carried out for diagnosis and maintenance at all temperatures exceeding 0 °C.