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2008 - MX-5 - Engine

NO.24 A/C IS ALWAYS ON/A/C COMPRESSOR RUNS CONTINUOUSLY [LF]



24

A/C IS ALWAYS ON OR A/C COMPRESSOR RUNS CONTINUOUSLY.

DESCRIPTION

A/C compressor magnetic clutch does not disengage.

POSSIBLE CAUSE

  • A/C compressor magnetic clutch engagement is stuck.

  • A/C relay is stuck closed.

  • Short to GND in wiring harness between A/C switch and PCM

  • Short to GND in wiring harness between A/C relay and PCM

  • Short circuit to battery power in A/C relay to magnetic clutch


Diagnostic procedure

STEP

INSPECTION

RESULTS

ACTION

1

Connect the M-MDS to the DLC-2.

Turn the ignition switch to the ON position (Engine off).

Retrieve any DTCs.

Are there any DTCs displayed?

Yes

DTC is displayed:

Go to the appropriate DTC inspection.

(See DTC TABLE [LF].)

No

No DTC is displayed:

Go to the next step.

2

Start the engine and idle it.

Turn the A/C switch on.

Remove the A/C relay.

Does the A/C magnetic clutch disengage?

Yes

Inspect for the following:

  • A/C relay is stuck closed.

  • Short to GND in wiring harness between A/C relay and PCM terminal 1I.

If both items normal, go to the next step.

No

Inspect if circuit between the A/C relay and magnetic clutch shorts to battery power circuit.

If the circuit is normal, inspect the magnetic clutch for stuck engagement or clearance.

3

Disconnect refrigerant pressure switch connector.

Start the engine and turn A/C switch on.

NOTE:

  • A/C should not work when disconnecting connector. If A/C remains working, short to GND circuit may be present.

Does the A/C remain working?

Yes

Inspect for short to GND in wiring harness between refrigerant pressure switch and PCM terminal 1AU.

No

Go to the next step.

4

Reconnect refrigerant pressure switch connector.

Turn off A/C switch.

NOTE:

  • A/C should not work when turning A/C switch off. If A/C remains working, short to GND circuit may be present.

Does A/C remain working?

Yes

Inspect following:

  • Short to GND in wiring harness between A/C switch and A/C amplifier

  • Short to GND circuit between A/C amplifier and refrigerant pressure switch

No

Inspect whether A/C switch is stuck closed.

5

  • Verify test results.

    • If normal, return to diagnostic index to service any additional symptoms.

      (See SYMPTOM DIAGNOSTIC INDEX [LF].)

    • If malfunction remains, inspect related Service Bulletins and/or On-line Repair 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 [LF].)




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