Diagnostic Aids

Perform this test when instructed during QUICK TEST or other test step. This test is intended to diagnose the following:

• A/C relay.
• High pressure switch.
• Harness circuits: ACR and HPS.
• PCM.

1. 1) Check Power A/C To Relay
   
   Turn ignition off. Disconnect A/C relay. Turn ignition on. Measure voltage of PWR circuit at A/C relay harness connector. See Fig 1. If voltage is greater than 10 volts, go to next step. If voltage is less than 10 volts, repair open PWR circuit (Blue wire). Restore all electrical connections and repeat QUICK TEST .
   Fig 1: Identifying WAC Relay Circuit & Harness Connector

   Courtesy of FORD MOTOR CO.
2. 2) Perform Relay Click Test
   
   Turn ignition off. Disconnect PCM and inspect connector for damage. Turn ignition on. Ground ACR circuit at PCM connector terminal No. 12 (Light Green wire). See CIRCUIT PIN IDENTIFICATION  table. If relay does not click, go to next step. If relay clicks when grounded, replace PCM. Restore all electrical connections and repeat QUICK TEST .
3. 3) Check ACR Circuit For Open
   
   Disconnect PCM. Disconnect A/C relay harness connector. Measure resistance of ACR circuit between A/C relay harness connector and PCM connector terminal No. 12 (Light Green wire). If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open ACR circuit (Light Green wire).
4. 4) Check ACR Circuit For Short
   
   Turn ignition off. Disconnect PCM. Disconnect A/C relay. Measure resistance between ACR relay circuit at PCM connector terminal No. 12 (Light Green wire) and ground. If resistance is greater than 10 k/ohms, replace relay. Restore all electrical connections and repeat QUICK TEST . If resistance is less than 10 k/ohms, repair short to ground in ACR circuit (Light Green wire). Restore all electrical connections and repeat QUICK TEST.
   NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 4) to step 10). No test procedures have been omitted.
5. 10) Check Ground At High Pressure Switch
   
   Turn ignition off. Disconnect A/C high pressure switch. Measure resistance between ground terminal (Black wire) at switch harness connector and chassis ground. See Fig 2. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open ground circuit. Restore all electrical connections and repeat QUICK TEST .
   Fig 2: Identifying HPS Switch Circuit & Harness Connector

   Courtesy of FORD MOTOR CO.
6. 11) Check Signal Circuit For Open
   
   Turn ignition off. Disconnect PCM. Measure resistance of high pressure switch circuit between PCM connector terminal No. 9 (Blue/Black wire) and signal circuit at A/C switch harness connector. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open circuit in Blue/Black wire. Restore all electrical connections and repeat QUICK TEST .
7. 12) Check Signal Circuit For Short
   
   Turn ignition off. Disconnect PCM. Measure resistance between high pressure switch circuit at PCM connector terminal No. 9 (Blue/Black wire) and ground. If resistance is greater than 10 k/ohms, go to next step. If resistance is less than 10 k/ohms, repair short to ground in signal circuit (Blue/Black wire). Restore all electrical connections and repeat QUICK TEST .
8. 13) Check A/C High Pressure Switch
   
   See A/C-HEATER SYSTEMS - VILLAGER article in AIR CONDITIONING & HEATING SERVICE & REPAIR manual for switch testing procedures. Replace switch as necessary. If switch tests okay, and no problem is found with circuit, replace PCM. Restore all electrical connections and repeat QUICK TEST .