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NO.24 A/C ALWAYS ON OR A/C COMPRESSOR RUNS CONTINUOUSLY [MZR-CD (RF Turbo)]

BME010300103295

24 | A/C ALWAYS ON OR A/C COMPRESSOR RUNS CONTINUOUSLY
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DESCRIPTION | • A/C compressor magnetic clutch does not disengage.
POSSIBLE CAUSE | • A/C compressor magnetic clutch stuck engagement • A/C relay is stuck closed • Improper A/C compressor magnetic clutch clearance • Short to GND circuit between A/C switch and PCM • Short to GND circuit between A/C relay and PCM
• A/C relay to magnetic clutch circuit shorts to battery power

Diagnostic Procedure

STEP | INSPECTION | RESULTS | ACTION
--- | --- | --- | ---
1 | Perform self-test function using WDS or equivalent. Turn the engine switch to the ON position. Retrieve any DTC. Is DTC displayed? | Yes | DTC is displayed: Go to the applicable DTC inspection. (See DTC TABLE [MZR-CD (RF Turbo)].) Communication error message is displayed: Inspect for the following:
• Open circuit between PCM control relay and PCM terminal 53 or 79
• Open circuit PCM control relay and PCM terminal 69
• PCM control relay stuck open
• Open or poor GND circuit (PCM terminal 65, 85, 103 or 104)
• Poor connection vehicle body GND
No | No DTC is displayed: Go to the applicable DTC inspection. (See DTC TABLE [MZR-CD (RF Turbo)].)
2 | Start the engine and run it at idle. Turn the A/C switch on. Remove the A/C relay. Does the A/C magnetic clutch disengage? | Yes | Inspect for the followings: • A/C relay is stuck closed • Short to GND circuit between A/C relay and PCM terminal 73 If both items are normal, go to the next step.
No | Inspect if circuit between the A/C relay and the magnetic clutch shorts to battery power circuit. If circuit is normal, inspect the magnetic clutch stuck engagement or clearance.
3 | Start the engine and turn the A/C switch on. Measure the voltage at PCM terminal 84 while disconnecting the refrigerant pressure switch connector.

  Note

  • PCM terminal 84 voltage should read B+ when disconnecting connector. If PCM terminal 84 voltage reading remains below 1.0 V, short to GND circuit may be present.
Is the voltage B+?

Yes
Inspect for short to GND circuit between the refrigerant pressure switch and PCM terminal 84.
No | Go to the next step.
4 | Reconnect the refrigerant pressure switch connector. Measure the voltage at PCM terminal 84 while turning off the A/C switch.

  Note

  • PCM terminal 84 voltage should read B+ when turning A/C switch off. If PCM terminal 84 voltage reading remains below 1.0 V, short to GND circuit maybe present.
Does voltage remain B+?

Yes
Inspect for the followings:
• Short to GND circuit between A/C switch and A/C amplifier.
• Short to GND circuit between A/C amplifier and refrigerant pressure switch.
No | Inspect for stuck closed A/C switch.
5 | Verify test results. • If normal, return to diagnostic index to service any additional symptoms. • If malfunction remains, replace the PCM. (See PCM REMOVAL/INSTALLATION [MZR-CD (RF Turbo)].)