A/C Relay: Notes

Fig 1: Diagnostic Communication For A/C Relay

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 on the basis of the A/C pressure and then requests a corresponding increase in the air mass/combustion. After a short delay the control module grounds pin 4, which is connected to the A/C relay.

The control module activates the relay only when the engine has been started.

Fig 2: A/C Relay Circuit Diagram

Courtesy of SAAB-SCANIA OF AMERICA, INC.