NO.24 A/C IS ALWAYS ON OR A/C COMPRESSOR RUNS CONTINUOUSLY [MZI-3.7]

id0103d2803000

24 | A/C IS ALWAYS ON OR A/C COMPRESSOR RUNS CONTINUOUSLY
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DESCRIPTION | • A/C compressor magnetic clutch does not disengage.
POSSIBLE CAUSE | • PCM and instrument cluster DTC is stored. • Short to power supply in wiring harness between A/C relay and magnetic clutch • Magnetic clutch engagement is stuck. • A/C relay malfunction • Short to ground in wiring harness between A/C relay and PCM • Short to ground in wiring harness between front climate control unit terminal 2A and instrument cluster • Climate control unit malfunction • Instrument cluster malfunction

Diagnostic procedure

STEP | INSPECTION | RESULTS | ACTION
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1 | Retrieve the PCM and instrument cluster DTCs using the M-MDS. (See ON-BOARD DIAGNOSTIC TEST [MZI-3.7].) (See DTC INSPECTION [INSTRUMENT CLUSTER].) Are there any DTCs displayed? | Yes | Go to the appropriate DTC inspection. (See DTC TABLE [MZI-3.7].) (See DTC TABLE [INSTRUMENT CLUSTER].)
No | Go to the next step.
2 | Start the engine and idle it. Turn the A/C switch on with blower switch is on. Remove the A/C relay. Does the magnetic clutch disengage? | Yes | Go to Step 4.
No | Go to the next step.
3 | Turn the ignition switch to the off position. Disconnect the magnetic clutch connector. Turn the ignition switch to the ON position. Measure the voltage at the magnetic clutch terminal A. Is the voltage B+? | Yes | Repair or replace suspected wiring harness and connector.
No | Replace the A/C compressor. (Magnetic clutch engagement is stuck.) (See A/C COMPRESSOR REMOVAL/INSTALLATION.)
4 | Inspect the A/C relay. (See RELAY INSPECTION.) Is there any malfunction? | Yes | Replace the A/C relay.
No | Go to the next step.
5 | Access the PCM PID ACCS using the M-MDS. (See ON-BOARD DIAGNOSTIC TEST [MZI-3.7].) Start the engine and idle it. Turn the A/C switch on and off with blower switch is on. Is the PID value always ON? | Yes | Go to the next step.
No | Inspect for short to ground in wiring harness between the following: • PCM terminal 1W and A/C relay Repair or replace suspected wiring harness and connector.
6 | Measure the voltage at the front climate control unit terminal 2A (wiring harness-side). Is the voltage always below 1.0 V? (See FRONT CLIMATE CONTROL UNIT INSPECTION.) | Yes | Go to the next step.
No | Replace the instrument cluster. (Instrument cluster always transmits A/C request signal from climate control unit to PCM.) (See INSTRUMENT CLUSTER REMOVAL/INSTALLATION.)
7 | Turn the ignition switch to the off position. Disconnect the instrument cluster and front climate control unit connectors. Inspect for continuity between front climate control unit terminal 2A (wiring harness-side) and body ground. Is there continuity? | Yes | Repair or replace suspected wiring harness and connector.
No | Replace the front climate control unit. (A/C request signal is always on.) (See FRONT CLIMATE CONTROL UNIT REMOVAL/INSTALLATION.)
8 | • Verify test results. ― If normal, return to diagnostic index to service any additional symptoms. (See SYMPTOM DIAGNOSTIC INDEX [MZI-3.7].) ― If malfunction remains, inspect related Service Information and perform repair or diagnosis. • If vehicle is repaired, troubleshooting completed. • If vehicle is not repaired or additional diagnostic information is not available, replace the PCM. (See PCM REMOVAL/INSTALLATION [MZI-3.7].)