A/C Signal: Description and Operation

View: A/C Signal Path Diagram:

PURPOSE
To provide the powertrain control module engine (PCME) with an input signal which coresponds with the A/C system (ON/OFF) demand from the heater A/C control unit. The system design allows the PCME to control the actual ON/OFF operation of the magnetic clutch on the A/C compressor.

OPERATION
The A/C signal is not directly connected to the air conditioning system. The A/C signal tells the PCME, "Turn the A/C ON or OFF". When the PCME receives the "A/C ON" signal, it (the PCME) determines if it should turn the A/C ON based on inputs from other systems and sensors such as;

- A/C Cut-Off Control System
- Engine Coolant Temperature Sensor

When the blower switch and the A/C switch are turned ON, power flows to PCME input terminal 1Q (BR wire). The PCME recognizes this signal as a demand for A/C ON operation. The PCME will control the ON/OFF operation of the A/C system from this point via the ground circuit for the air conditioner relay. The ground circuit for the A/C relay connects to PCME terminal 1J (L/B wire).