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Test D7 - WAC

Fig 1: 2.9L Truck WOT A/C Cut-Out Circuits
G120757
  1. No A/C: Check For Voltage at A/C Clutch. Check all A/C related fuses in fuse panel before proceeding with this test. Use only DVOM, not diagnostic tester, for this step. Disconnect A/C clutch harness connector. Turn A/C switch to "A/C" position. Set DVOM on 20 volt scale. Start engine and wait 10 seconds. Measure voltage between the power side of the A/C clutch harness connector and negative battery terminal. If voltage is greater than 10.5 volts, EEC-IV system is okay, diagnose A/C clutch system. If voltage is less than 10.5 volts, go to step 5).
  2. Check Voltage at A/C De-Icing Switch. With key off, disconnect A/C clutch harness. Disconnect A/C de-icing switch. Turn A/C switch to ON position. Set DVOM to 20-volt scale. Start engine and wait 10 seconds. Measure voltage between both Power-from-WAC relay circuits at the A/C de-icing switch harness connector to chassis ground. If both voltages are greater than 10.5 volts, turn key off and go to step 4). If both voltages are not greater than 10.5 volts, reconnect A/C clutch harness and go to next step.
    Fig 2: A/C De-Icing Switch
    G120759
  3. Check Continuity From WAC Relay to De-Icing Switch. Turn key off, and disconnect A/C de-icing switch. Set DVOM on 200-ohm scale. Measure resistance between Power-to-Clutch circuit on the WAC relay harness connector and both Power-from-WAC relay circuits on the A/C de-icing switch harness connector. If both resistances are less than 5 ohms, go to step 6). If both resistances are not less than 5 ohms, repair open circuit, reconnect components and retest system.
    Fig 3: WAC Relay Harness Connector
    G120760
  4. Check Continuity From A/C De-Icing Switch to A/C Clutch. With key off, disconnect A/C clutch harness. Set DVOM on 200-ohm scale. Measure resistance between power side of A/C clutch harness connector and Power-to-Clutch terminal at A/C de-icing switch. If resistance is less than 5 ohms, check ground circuit to A/C de-icing switch. If circuit is okay, problem is not EEC-IV related. Service or replace A/C de-icing switch. If resistance is greater than 5 ohms, check operation of 3-way pressure switch. If 3-way pressure switch is okay, repair open circuit and retest system.
  5. Checking Continuity of Power-to-Clutch Circuit. Turn key off and wait 10 seconds. Set DVOM on 200-ohm scale. Disconnect A/C clutch harness and harness from WAC relay. Measure resistance between power side of A/C clutch harness connector and Power-to-Clutch terminal pin at WAC relay. If resistance is less than 5 ohms, reconnect A/C clutch and go to next step. If resistance is more than 5 ohms, service open circuit and re-test system.
  6. Checking Power on A/C Demand Circuit. With KOEO and WAC relay disconnected, turn on A/C switch. Set DVOM to 20-volt scale. Measure voltage between A/C demand input terminal pin at WAC relay and ground. If voltage is greater than 10.5 volts, go to next step. If voltage is less than 10.5 volts, check switch operation, repair open circuit and retest system.
  7. Checking WAC Circuit For Short to Ground. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector and WAC relay. Inspect and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200K-ohm scale. Measure resistance between WAC circuit at WAC relay and chassis ground. If resistance is greater than 10K ohms, go to step 10). If resistance is less than 10K ohms, repair short and retest system.
  8. Checking A/C Fan Controller Ground Circuit. With key off and A/C fan controller disconnected, set DVOM on 200-ohm scale. Disconnect ECA. Measure resistance between ground circuit at A/C fan controller harness connector and chassis ground. If resistance is less than 5 ohms, go to next step. If resistance is more than 5 ohms, repair open circuit and retest system.
  9. Checking For Voltage to A/C Fan Controller. With key on, ECA and A/C fan controller disconnected, set DVOM on 20-volt scale. Measure voltage between ignition switch RUN circuit at the A/C fan controller harness connector and chassis ground. If voltage is greater than 10.5 volts, go to next step. If voltage is less than 10.5 volts, repair open circuit, reconnect ECA and A/C controller and re-test system.
  10. Checking WAC Relay. Turn key off and wait 10 seconds. Leave ECA disconnected and reconnect WAC relay. Set DVOM on 20-volt scale. With KOEO and A/C on, measure voltage between power side of A/C clutch harness connector and battery negative terminal. If voltage is greater than 10.5 volts, replace ECA, reconnect A/C clutch and retest system. If voltage is less than 10.5 volts, replace WAC relay. Retest system.
  11. Checking A/C Output at WOT. Enter OUTPUT STATE CHECK, see OUTPUT STATE CHECK under DIAGNOSTIC AIDS. Use a VOM or DVOM meter for this test. Turn key off and wait 10 seconds. Set DVOM on 20-volt scale. Connect DVOM negative lead to STO at Self-Test connector and positive lead to positive battery terminal. Jumper STI to SIG RTN at Self-Test connector. Perform KOEO SELF-TEST until completion of Continuous Memory Code sequence. Meter will indicate less than one volt when test is complete. Depress and release throttle. If voltage increases to 10.5 volts or more, remain in OUTPUT STATE CHECK and go to next step. If voltage does not increase to 10.5 volts, leave test equipment connected and go to test D16, step 2).
  12. System Identification. If vehicle is equipped with WAC relay, go to next step. If vehicle is equipped with A/C fan controller, go to step 17). (2.9L MPFI vehicles are equipped with WAC Relay).
  13. Checking VPWR to Relay. With vehicle in OUTPUT STATE CHECK, disconnect harness from WAC relay and set DVOM on 20-volt scale. Measure voltage between VPWR circuit at the WAC relay harness connector and chassis ground. If voltage is greater than 10.5 volts, go to next step. If voltage is less than 10.5 volts, repair open circuit, remove test equipment, and retest system.
  14. Checking WAC System For Cycling. With vehicle in OUTPUT STATE CHECK, disconnect harness from WAC relay and set DVOM on 20-volt scale. Connect positive test lead to VPWR circuit and negative test lead to WAC circuit at WAC relay harness connector. Check DVOM while depressing and releasing throttle several times, to cycle system. If voltage cycles from high to low, replace WAC relay and retest system. If voltage does not cycle, remove test leads and go to next step.
  15. Checking Continuity of WAC Circuit. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect and repair any damaged wiring. Install breakout box, leaving ECA and WAC relay disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 54 and WAC circuit at relay harness connector. If reading is 5 ohms or more, repair open circuit and repeat QUICK TEST. If reading is less than 5 ohms, go to next step.
  16. Checking For Short to Power. Turn key off. Leave breakout box installed, ECA and WAC relay disconnected. Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 54 and test pins No. 37 and 57 at breakout box. If any reading is less than 10K ohms, repair short circuit and repeat QUICK TEST. If all readings are 10K ohms or more, replace ECA and retest system.
  17. Check WAC Cycling. With vehicle in OUTPUT STATE CHECK, disconnect A/C fan controller and set DVOM on 20-volt scale. Connect DVOM positive test lead to ignition run circuit and negative test lead to WAC circuit at A/C fan controller harness connector. Check DVOM while depressing and releasing throttle several times, to cycle system. If voltage cycles from high to low, replace A/C fan controller and re-test system. If voltage does not cycle, remove jumper and go to next step.
  18. Checking Continuity of WAC Circuit. Turn key off. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA and fan controller disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 54 and WAC circuit at WAC relay harness connector. If reading is 5 ohms or more, repair open in harness and repeat QUICK TEST. If reading is less than 5 ohms, go to next step.
  19. Checking For Short to Power. Turn key off. Install breakout box, leaving ECA and A/C fan controller disconnected. Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 54 and test pins No. 37 and 57 at the breakout box. If all readings are greater than 10K ohms, replace ECA, reconnect A/C fan controller and retest system. If any reading is 10K ohms or less, repair short to power and repeat QUICK TEST. If symptom is still present, replace ECA.
  20. Cycle A/C Demand Switch. Turn key off and wait 10 seconds. Disconnect 60-pin ECA connector. Inspect wiring and pins for damage and repair as necessary. Install breakout box, leaving ECA disconnected. Set DVOM on 20-volt scale. With KOEO, connect DVOM positive test lead to test pin No. 43 and negative test lead to test pin No. 40. If voltage goes high and low as switch is cycled, replace ECA and repeat QUICK TEST. If voltage does not cycle, go to next step.
  21. Checking Continuity of A/C Demand (ACD) Circuit. Turn key off and wait 10 seconds. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 43 at the breakout box and A/C demand switch. If resistance is greater than 5 ohms, repair open in A/C demand circuit and rerun QUICK TEST. If resistance is less than 5 ohms, EEC-IV system is okay.
  22. Checking A/C Demand (ACD) Circuit For Short to Power. Turn key off. Disconnect WAC relay or A/C fan controller. Disconnect ECA and install breakout box. With ACD switch "OFF", set DVOM on 20 volt scale. Turn key on. Measure voltage between test pin No. 24 at breakout box and chassis ground. If voltage is less than one volt EEC-IV system is okay. If voltage is more than one volt, check operation of A/C demand switch, repair short circuit and retest system.
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