S80 T6 L6-2.9L Turbo VIN 91 B6294T (2002)
When the terminal (#85) is grounded, the relay is activated and a number of components are powered via the relay terminal (#87).
The engine control module (ECM) can diagnose the main relay.
The main relay is in the relay/fusebox in the engine compartment.
Air conditioning (A/C) relay
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:
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full load acceleration
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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.
Fuel pump (FP) relay
