Diagnostic Procedure

WARNING: This page is about a different car, the 2005 Mazda MX-5 Miata. However, it is still accessible from the selected car via links, so may be relevant.

AIR CONDITIONER DOES NOT OPERATE EVEN THROUGH AIRFLOW IS IN DEFROSTER MODE OR HEAT/DEFROSTER MODE - DIAGNOSTIC PROCEDURE

STEP	INSPECTION		ACTION
1	INSPECT COOL AIR BLOW OUT When both A/C and fan switches are on, is cool air discharged?	Yes	Go to next step.
1		No	Go to Step 1 of troubleshooting index No.7.
*2	CHECK TO SEE WHETHER MALFUNCTION IN A/C SWITCH CIRCUIT IS AN OPEN CIRCUIT OR A SHORT TO +B Turn both A/C switch and fan switch off. Set airflow mode control dial to DEFROSTER mode or HEAT/DEFROSTER mode. Disconnect A/C amplifier connector. Turn ignition switch to ON position. Test voltage at A/C amplifier terminal B (A/C signal). Is voltage approximately 12 V ?	Yes	Go to next step.
*2		No	Go to Step 5.
*3	INSPECT WIRING HARNESS BETWEEN A/C AMPLIFIER AND A/C SWITCH FOR SHORT TO +B Remove climate control unit. Disconnect A/C switch connector. Turn ignition switch to ON position. Test voltage at A/C switch terminal A (A/C signal). Is voltage approximately 12 V ?	Yes	Repair wiring harness between A/C amplifier and A/C switch, then go to Step 9.
*3		No	Go to next step.
*4	CHECK FOR SHORT CIRCUIT IN +B CLIMATE CONTROL UNIT (A/C SWITCH) Reconnect A/C switch connector. Set airflow mode control dial to something other than DEFROSTER mode and HEAT/DEFROSTER mode Turn ignition switch to ON position. Test voltage at A/C switch terminal A (A/C signal). Is voltage approximately 12 V ?	Yes	Replace climate control unit (short to +B in A/C switch), then go to Step 9.
*4		No	Recheck malfunction symptoms.
5	INSPECT CLIMATE CONTROL UNIT A/C SWITCH INSTALLATION Remove climate control unit. Is A/C switch in climate control unit installed securely?	Yes	Go to next step.
5		No	Install A/C switch securely, then go to Step 9.
6	CHECK FOR OPEN CIRCUIT IN CLIMATE CONTROL UNIT (A/C SWITCH) Set airflow mode control dial to DEFROSTER mode or HEAT/DEFROSTER mode. Is there continuity between climate control unit (2-pin) terminals A and B?	Yes	Go to Step 8.
6		No	Go to next step.
7	VISUALLY INSPECT A/C SWITCH IN CLIMATE CONTROL UNIT Is A/C switch free of damage?	Yes	Recheck malfunction symptoms
7		No	Replace climate control unit (open circuit in A/C switch), then go to Step 9.
*8	INSPECT WIRING HARNESS BETWEEN A/C SWITCH AND RESISTOR FOR CONTINUITY Verify that A/C switch and fan switch are off. Turn ignition switch to ON position. Test voltage at A/C switch terminal B (A/C signal). Is voltage approximately 12 V ?	Yes	Inspect wiring harness between A/C amplifier and A/C switch, then go to next step.
*8		No	Repair wiring harness between A/C switch and resistor, then go to next step.
9	CONFIRM THAT MALFUNCTION SYMPTOM DOES NOT RECUR AFTER REPAIR Does windshield become clear in DEFROSTER mode or HEAT/DEFROSTER mode?	Yes	Troubleshooting completed. Explain repairs to customer.
9		No	Recheck malfunction symptoms, then repeat from Step 1 if malfunction recurs.