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.

NO COOL AIR - DIAGNOSTIC PROCEDURE

STEP	INSPECTION		ACTION
1	INSPECT AIR BLOW OUT Is air discharged?	Yes	Go to next step.
1	INSPECT AIR BLOW OUT Is air discharged?	No	Go to Step 1 of troubleshooting indexes No.1, 2.
2	INSPECT A/C COMPRESSOR OPERATION Start engine. Turn both A/C switch and fan switch on. Does A/C compressor operate?	Yes	Go to next step.
2		No	Go to Step 4.
3	CHECK TO SEE WHETHER VENT AIR TEMPERATURE IS NORMAL OR NOT Is vent air temperature 6°C {43°F} or less ?	Yes	Operation is normal. (To prevent evaporator within cooling unit from freezing, A/C compressor stops right away when vent air temperature is 6°C {43°F} or less.
3		No	Go to Step 1 of troubleshooting index No.6.
4	INSPECT REFRIGERANT AMOUNT Inspect refrigerant amount. (See REFRIGERANT CHARGE CHECK ) Is it okay?	Yes	Go to next step.
4		No	Adjust refrigerant to specified level, then go to Step 27.
5	INSPECT A/C SWITCH INDICATOR LIGHT Does A/C switch indicator light illuminate?	Yes	Go to Step 8.
5		No	Go to next step.
*6	INSPECT WIRING HARNESS BETWEEN A/C 10A FUSE AND A/C SWITCH FOR CONTINUITY Turn ignition switch to ON position. Test voltage at A/C switch terminal C (IG2 signal). Is voltage approximately 12 V ?	Yes	Go to next step.
*6		No	Repair wiring harness between A/C 7.5 A fuse and A/C switch, then go to Step 27.
*7	INSPECT A/C SWITCH Inspect A/C switch. (See CLIMATE CONTROL UNIT INSPECTION ) Is it okay.	Yes	Inspect wiring harness between A/C switch and fan switch, then go to Step 27.
*7		No	Replace A/C switch, then go to Step 27.
*8	CHECK TO SEE IF MALFUNCTION IS IN A/C AMPLIFIER SYSTEM OR ELSEWHERE Turn ignition switch to LOCK position. Disconnect refrigerant pressure switch connector. Turn ignition switch to ON position. Set fan switch to first speed. Test voltage at the following terminal of refrigerant pressure switch connector (harness-side). Terminal B (A/C signal) Is voltage approximately 12 V when A/C switch is off and 0 V when it is on?	Yes	Go to Step 15.
*8		No	Go to next step.
*9	INSPECT WIRING HARNESS BETWEEN A/C 10A FUSE AND A/C AMPLIFIER FOR CONTINUITY Turn A/C switch off. Test voltage at A/C amplifier terminal A (IG2 signal). Is voltage approximately 12 V ?	Yes	Go to next step.
*9		No	Repair wiring harness between A/C 7.5 A fuse and A/C amplifier, then go to Step 27.
*10	INSPECT WIRING HARNESS BETWEEN REFRIGERANT PRESSURE SWITCH AND A/ C AMPLIFIER FOR CONTINUITY Measure voltage at A/C amplifier terminal C (A/C signal). Is voltage approximately 12 V when A/C switch is off and 0 V when it is on?	Yes	Repair wiring harness between refrigerant pressure switch and A/C amplifier, then go to Step 27.
*10		No	Go to next step.
11	INSPECT WIRING HARNESS BETWEEN REFRIGERANT PRESSURE SWITCH AND A/ C AMPLIFIER FOR SHORT TO GROUND Turn ignition switch to LOCK position. Disconnect A/C amplifier connector. Inspect for continuity at the following terminal between A/C amplifier connector (on wiring harness side) and ground. Terminal C (A/C signal) Is there continuity?	Yes	Repair wiring harness between refrigerant pressure switch and A/C amplifier, then go to Step 27.
11		No	Go to next step.
*12	INSPECT A/C AMPLIFIER Inspect A/C amplifier. Is it okay?	Yes	Go to next step.
*12	INSPECT A/C AMPLIFIER Inspect A/C amplifier. Is it okay?	No	Replace A/C amplifier, then go to Step 27.
*13	INSPECT WIRING HARNESS BETWEEN A/C AMPLIFIER AND A/C SWITCH FOR SHORT TO +B Turn A/C switch on. Turn fan switch off. Measure voltage at A/C switch terminal B (A/ C signal). Is voltage approximately 12 V ?	Yes	Repair wiring harness between A/C amplifier and A/C switch, then go to Step 27.
*13		No	Go to next step.
14	CHECK TO SEE WHETHER MALFUNCTION (SHORT TO GROUND) IS IN A/C SWITCH OR WIRING HARNESS (BETWEEN A/C AMPLIFIER AND A/C SWITCH) Turn ignition switch to LOCK position. Disconnect A/C switch connector. Check for continuity at the following terminal between A/C switch connector (harness-side) and ground. Terminal B (A/C signal) Is there continuity?	Yes	Repair wiring harness between A/C amplifier and A/C switch, then go to Step 27.
14		No	Replace A/C switch, then go to Step 27.
*15	CHECK TO SEE MALFUNCTION IS IN PCM AND WIRING HARNESS (BETWEEN PCM AND REFRIGERANT PRESSURE SWITCH FOR CONTINUITY) OR ELSEWHERE Test voltage at refrigerant pressure switch terminal B (harness-side) (A/C signal). Is voltage approximately 12 V ?	Yes	Go to Step 17.
*15		No	Go to next step.
*16	CHECK TO SEE IF MALFUNCTION IS IN PCM OR WIRING HARNESS (CHECK BETWEEN PCM AND REFRIGERANT PRESSURE SWITCH FOR CONTINUITY) Test voltage at PCM terminal 4F (A/C signal). Is voltage approximately 12 V ?	Yes	Repair wiring harness between PCM and refrigerant pressure switch, then go to Step 27.
*16		No	Inspect PCM, then go to Step 27.
17	CHECK TO SEE IF MALFUNCTION IS IN REFRIGERANT PRESSURE SWITCH OR ELSEWHERE When refrigerant pressure switch terminals A and B (harness-side) are shorted, is cool air discharged?	Yes	Inspect refrigerant pressure switch, then go to Step 27.
17		No	Undo short circuit, reconnect refrigerant pressure switch connector, then go to next step.
*18	CHECK TO SEE WHETHER MALFUNCTION IS IN PCM SYSTEM OR ELSEWHERE Does magnetic clutch operate when terminal A (IG2 signal) of A/C relay connector is grounded?	Yes	Undo short circuit, then go to next step.
*18		No	Go to Step 22.
*19	INSPECT WIRING HARNESS BETWEEN A/C RELAY AND PCM FOR CONTINUITY Turn A/C switch off. Measure voltage at PCM terminal 2K (IG2 signal). Is voltage approximately 12 V ?	Yes	Go to next step.
*19		No	Repair wiring harness between A/C relay and PCM, then go to Step 27.
*20	INSPECT INPUT SIGNAL FOR PCM'S A/C CUT-OFF CONTROL Inspect input signal components (crankshaft position sensor, engine coolant temperature sensor, power steering pressure switch, throttle position sensor, neutral switch (MT), transaxle range switch (AT), including wiring harness of PCM (A/C cut-off control). Are they okay?	Yes	Go to next step.
*20		No	Replace input signal components, then go to Step 27.
21	INSPECT COOLING FAN CONTROL SYSTEM AND CONDENSER FAN CONTROL SYSTEM Is coolant system operating properly? Is it okay?	Yes	Inspect PCM, then go to Step 27.
21		No	Check for cause.
*22	CHECK TO SEE IF MALFUNCTION IS IN MAGNETIC CLUTCH AND THERMAL PROTECTOR OR ELSEWHERE Test voltage at magnetic clutch thermal protector terminal A (A/C control signal). Is voltage approximately 12 V ?	Yes	Go to next step.
*22		No	Go to Step 24.
*23	INSPECT MAGNETIC CLUTCH Inspect magnetic clutch. (See MAGNETIC CLUTCH INSPECTION ) Is it okay?	Yes	Replace thermal protector, then go to Step 27.
*23		No	Replace magnetic clutch stator, then go to Step 27.
24	INSPECT FUSES Check the following fuses: A/C 7.5 A fuse AD FAN 20 A fuse Are they okay?	Yes	Go to next step.
24		No	Replace fuse, then go to Step 27.If fuse burns out right away, go to next step.
*25	INSPECT WIRING HARNESS BETWEEN FUSE BLOCK AND A/C RELAY FOR CONTINUITY Test voltage at the following A/C relay terminals: Terminal A (IG2 signal) Terminal C (A/C control signal) Is voltage approximately 12 V ?	Yes	Go to next step.
*25		No	Repair wiring harness between A/C 7.5 A fuse or AD FAN 20 A fuse and A/C relay, then go to Step 27.
*26	CHECK TO SEE IF MALFUNCTION IS IN A/C RELAY OR WIRING HARNESS (CHECK BETWEEN A/C RELAY AND THERMAL PROTECTOR FOR CONTINUITY) Test voltage at A/C relay terminal D (A/C control signal). Is voltage approximately 12 V ?	Yes	Repair wiring harness between A/C relay and thermal protector, then go to next step.
*26		No	Replace A/C relay, then go to next step.
*27	VERIFY THAT MALFUNCTION SYMPTOM DOES NOT OCCUR AFTER REPAIR Is cool air discharged? (Is refrigerant system performance test result correct?)	Yes	Troubleshooting completed. Explain repairs to customer.
*27		No	Recheck malfunction symptoms, then repeat from Step 1 if malfunction recurs.