Diagnostic procedure

WARNING: This page is about a different car, the 2005 Mazda RX-8. However, it is still accessible from the selected car via links, so may be relevant.

NO.24 A/C IS ALWAYS ON OR A/C COMPRESSOR RUNS CONTINUOUSLY DIAGNOSTIC PROCEDURE

STEP	INSPECTION	RESULTS	ACTION
1	Connect the WDS or equivalent 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 applicable DTC inspection. (See DTC TABLE .)
1		No	No DTC is displayed: Go to the next step.
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 following: The A/C relay is stuck closed. Short to GND circuit between the A/C relay and PCM terminal 5AA. If both items normal, go to the next step.
2		No	Inspect if the circuit between A/C relay and the magnetic clutch shorts to the battery power circuit. If the circuit is normal, inspect the magnetic clutch for stuck engagement or clearance.
3	Disconnect the refrigerant pressure switch connector. Start the engine and turn the A/C switch on. NOTE: The A/C should not work when disconnecting the connector. If the A/C remains working, a short to GND circuit may be present. Does the A/C remain working?	Yes	Inspect for short to GND circuit between refrigerant pressure switch and PCM terminal 4W.
3		No	Go to the next step.
4	Reconnect refrigerant pressure switch connector. Turn off the A/C switch. NOTE: The A/C should not work when turning the A/C switch off. If the A/C remains working, a short to GND circuit may be present. Does the A/C remain working?	Yes	Inspect the following: Short to GND circuit between the A/C switch and the A/C amplifier Short to GND circuit between the A/C amplifier and the refrigerant pressure switch
4		No	Inspect whether the A/C switch is stuck closed.
5	Verify test results. If normal, return to the diagnostic index to service any additional symptoms. If the malfunction remains, inspect the related Service Bulletins and/or the On-line Repair Information and perform the repair or diagnosis.