System Relay: Description and Operation

A/C Relay

Diagram:

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.

Diagnostics
^ If there is an open circuit or short circuit to ground, diagnostic trouble code P1656 will be generated.
^ If there is a short circuit to B+, diagnostic trouble code P1657 will be generated.

NOTE: The A/C request from DICE can be read with the diagnostic tool.