Air Conditioning (A/C)

WARNING: This page is about a different car, the 2002 Volvo C70, 2001 Volvo C70, 2000 Volvo C70, 1999 Volvo C70, and 1998 Volvo C70. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Identifying A/C Relay, A/C Compressor Solenoid Clutch And Pressure Switch (Pressostat)

Courtesy of VOLVO CARS OF NORTH AMERICA.

The A/C relay (2/22) is activated if the A/C switch is pressed, the blower fan is operating and the engine control module (ECM) confirms it. Power is supplied to the A/C compressor solenoid clutch (8/3) and the cycling of the compressor can be controlled by the pressure switch (Pressostat) (7/53) normally.

In the following circumstances the compressor is disengaged to prevent it operating when full power is required, or when there is a risk of overheating:

full acceleration; at wide open throttle (WOT) the engine control module (ECM) shuts the compressor down for a maximum of 15 seconds and a minimum of 3 seconds
risk of overheating. If coolant temperature is above approximately 125°C the air conditioning (A/C) compressor is prevented from operating in order to reduce engine load and avoid further overheating.
if pressure exceeds approximately 3000 kPa.

The engine control module (ECM) also prevents the compressor from engaging before the engine has started properly. The air conditioning (A/C) compressor cannot start until the engine has been started for approximately 5-15 seconds.