A/C relay: Notes

Fig 1: Identifying A/C Relay

Courtesy of SAAB-SCANIA OF AMERICA, INC.

Fig 2: A/C Relay Circuit Diagram

Courtesy of SAAB-SCANIA OF AMERICA, INC.

When the A/C compressor is activated from the ACC or MCC and all other condition have been fulfilled, DICE will send bus information "A/C ON". The value is used by Trionic T7.

The control module then calculates the impending torque requirement of the compressor based on the A/C pressure and subsequently requests a corresponding increase in the air mass/combustion. After a short delay, the control module will ground pin 4, which is connected to the A/C relay.

The control module activates the relay only after the engine has started.