Heating and ventilation (with A/C) – circuit operation

HEATING AND VENTILATION (WITH A/C) – CIRCUIT OPERATION

A/C Request

This signal is active low and sends a request to the ECM to switch on the air-conditioning system.

A/C Grant

This signal is active low and sends a signal to the HEVAC ECU to acknowledge the request signal and that it is ready for the load to be switched on by the HEVAC system.

Pressure switch 1 (Trinary switch)

This switch is in parallel with two components, the condensor fans and the compressor clutch which are both normally short circuit. If the pressure is too high or too low, the switch will open and cut the feed to the clutch to prevent damage to the system. With the third setting, at a specific pressure the switch is shorted and changes the condenser fan mode from series to parallel.

Pressure switch 2 (Single switch)

The switch is normally open circuit. At a specific pressure, the switch is shorted and allows the condenser fans to turn on.

Left/Right Recirculation motors

These motors control the flaps on the blower motor modules. The flaps should be in one of two positions, either fully open or fully closed.

Left/Right Blower modules

The blowers have a permanent 12V feed to them. The speed of the motors is determined by the control lines which go to the motors. The motors also provide a voltage feedback to the HEVAC ECU to determine the actual voltage at the motors but also to show if there are any faults.

Left/Right Blend and Distribution Motors

These motors are controlled by the HEVAC ECU which provides power to the motors, which in turn report back their actual positions to the HEVAC ECU.