Test D: A/C Does Not Operate/Does Not Operate Correctly

Start engine. Turn on A/C. If compressor clutch engages, go to A/C SYSTEM PERFORMANCE under TESTING. If compressor clutch does not engage, go to next step.
Turn ignition off. Disconnect A/C compressor clutch harness connector located in engine compartment. Turn ignition on. Measure voltage between ground and clutch harness connector White/Orange wire terminal. If battery voltage exists, go to next step. If battery voltage does not exist, go to step 7 .
Measure resistance between ground and clutch harness connector Black wire terminal. If resistance is 5 ohms or less, go to next step. If resistance is more than 5 ohms, repair open in Black wire. Retest system.
Turn ignition off. Measure resistance between White/Orange wire terminal and Black wire terminal of A/C clutch connector. If resistance is more than 10 k/ohms, replace compressor clutch. Retest system. If resistance is 10 k/ohms or less, go to next step.
Measure clutch air gap at 3 equally spaced places between clutch hub and pulley. If air gap is .018-.033" (.45-.85 mm), go to next step. If air gap is not within specifications, adjust air gap.
Discharge A/C system using, approved recycling/recovery equipment. Remove A/C manifold and tube assembly. With A/C clutch disengaged, rotate compressor shaft and note torque required to rotate shaft one revolution. If torque required exceeds 89 INCH lbs. (10 N.m), replace A/C compressor. Retest system. If torque required is less than specified, replace compressor clutch. Retest system.
Disconnect PCM harness connector C275. Turn ignition on. Connect a 10-amp fused jumper wire between ground and terminal No. 12 (Light Green wire) of PCM harness connector. Measure voltage between ground and compressor clutch harness connector White/Orange terminal. If battery voltage exists, go to step 13 . If battery voltage does not exist, go to next step.
Turn ignition off. Disconnect A/C relay harness connector (located in engine compartment relay box). Connect ohmmeter to terminals No. 1 and 2. See Fig 1 . Resistance should be 50-100 ohms. Connect ohmmeter between terminals No. 3 and 4. Continuity should exist. Connect ohmmeter between terminals No. 3 and 5, No. 2 and 3, No. 2 and 4, and No. 2 and 5. Continuity should not exist.
Connect battery voltage to terminals No. 3 and 1, and ground terminal No. 2. Measure voltage between terminals No. 2 and 5. Battery voltage should exist. Disconnect power from terminal No. 1 and measure voltage between terminals No. 2 and 4. Battery voltage should exist. If relay fails any test, replace relay. If relay passes all tests, go next step. Retest system.

Fig 1: Identifying A/C Relay Terminals
Courtesy of FORD MOTOR CO.
Turn ignition on. Measure voltage between ground and terminal No. 3 (Gray wire) of A/C relay socket, under left side of dashboard in Central Junction Box (CJB). If battery voltage exists, go to next step. If battery voltage does not exist, repair open in Gray wire between terminal No. 13 of Battery Junction Box (BJB) and terminal No. 3 of A/C relay socket. Retest system.
Measure voltage between ground and terminal No. 2 (Blue wire) of A/C relay socket, under left side of dashboard in Central Junction Box (CJB). If battery voltage exists, go to next step. If battery voltage does not exist, repair open in Blue wire between terminal No. 12 of Battery Junction Box (BJB) and terminal No. 2 of A/C relay in CJB. Retest system.
Turn ignition off. Measure resistance of White/Orange wire between terminal No. 5 of A/C relay under left side of dashboard in Central Junction Box (CJB) and terminal No. 2 of A/C clutch compressor harness connector. If resistance is 5 ohms or less, replace A/C compressor clutch. If resistance is more than 5 ohms, repair appropriate wire. Retest system.
Connect manifold gauge set to service ports. If pressure reads between 50-250 psi (3.5-17.5 kg/cm² ), go to next step. If reading is not within specifications, check for refrigerant leaks.
Measure resistance between ground and terminal No. 21 (White/Red wire) of PCM harness connector. If resistance 5 ohms or less, replace PCM. Retest system. If resistance is more than 5 ohms, go to next step.
Measure resistance between ground and terminal No. 9 (Blue/Black wire) of PCM harness connector. If resistance is 10 k/ohms or less, go to next step. If resistance is more than 10 k/ohms, go to step 16 .
Disconnect A/C high pressure cut-off switch harness connector. Measure resistance between ground and terminal No. 9 (Blue/Black wire) of PCM harness connector. If resistance is more than 10 k/ohms, replace A/C high pressure cut-off switch. Retest system. If resistance is 10 k/ohms or less, repair open in Blue/Black wire between PCM and dual pressure switch. Retest system.
Measure resistance between ground and terminal No. 1 (Brown wire) of dual pressure switch harness connector. If resistance is 5 ohms or less, replace dual pressure switch. Retest system. If resistance is more than 5 ohms, go to next step.
Disconnect A/C compressor cycling switch harness connector. Measure resistance between ground and terminal No. 2 (Brown/White wire) of A/C cycling switch harness connector. If resistance is 5 ohms or less, go to next step. If resistance is more than 5 ohms, go to step 19 .
Measure resistance of Brown wire between A/C compressor cycling switch connector and terminal No. 1 of dual pressure switch harness connector. If resistance is 5 ohms or less, replace A/C cycling switch. Retest system. If resistance is more than 5 ohms, repair open in Brown wire. Retest system.
Disconnect EATC module harness connector C2028a. Measure resistance of Brown/White wire between terminal No. 10 of EATC module connector C2028a and terminal No. 2 of A/C cycling switch connector. If resistance is 5 ohms or less, replace EATC module. Retest system. If resistance is more than 5 ohms, repair open in Brown/White wire. Retest system.