Checking Air Conditioning (A/C) Compressor Control

Check, Cables And Components









NOTE: This test is designed for the electrical circuit between ECC/MCC control module and engine control module (ECM) via the low pressure switch.

Check the connectors on the ECC/MCC control module, low pressure switch and engine control module (ECM) for contact resistance and oxidation according to Checking wiring and terminals - Permanent faults Checking Wiring and Terminals

Check signal cable between ECC control module #A3 (MCC control module #B22) and engine control module (ECM) for an open-circuit according to Checking wiring and terminals - Permanent faults Checking Wiring and Terminals

At normal system pressure in the Air Conditioning (A/C) system the low pressure switch should be closed (approximately 0 ohm). If the pressure is too low the switch is open (infinite resistance).

Remedy as necessary.

Other information:

- Connection of breakout box to ECC control module Connection of Breakout Box ECC
- Connection of breakout box to MCC control module Connection of Breakout Box MCC

- Voltage on the cable should be 0 - 2V below air conditioning battery voltage when the control module demands Air Conditioning (A/C), approximately 0 V when Air Conditioning (A/C) is not demanded.

For other signals refer to Signal Specifications ECC Signal Specification ECC and Signal Specification MCC Signal Specification MCC