Air conditioning (A/C) relay

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2006 Volvo S80, 2005 Volvo S80, 2004 Volvo S80, 2003 Volvo S80, and 2002 Volvo S80. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Identifying Air Conditioning (A/C) Relay

Courtesy of VOLVO CARS OF NORTH AMERICA.

The air conditioning (A/C) relay controls the A/C compressor. When the climate control module (CCM) requests A/C control, a signal is transmitted to the engine control module (ECM) via the controller area network (CAN) to activate the relay. The engine control module (ECM) temporarily deactivates the relay in the event of:

full load acceleration
too high engine coolant temperature.

The relay is mechanical. It has a closing / breaking function and is supplied with power from the system relay.

In the rest position the circuit in the relay is open.

The system relay supplies the coil and the relay with power. The relay activates when the coil is grounded in the engine control module (ECM), the circuit closes and the A/C compressor is supplied with power via the relay voltage output.

The relay coil is grounded (signal) when the engine control module (ECM) receives a signal via the Controller area network (CAN) from the climate control module (CCM) to activate the relay and start the compressor.