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Test D7 - Wot-A/C Cut-Out (WAC) & A/C Demand Switch

Fig 1: 2.9L MPFI & 3.0L MPFI WOT A/C Cut-Out Circuits
G72370
Fig 2: 2.3L MPFI Truck Engine WOT A/C Cut-Out Circuits
G72371
Fig 3: 1.9L CFI & 1.9L MPFI Engine WOT A/C Cut-Out Circuits
G72372
Fig 4: 2.3L HSC MPFI Engine WOT A/C Cut-Out Circuits
G72373
Fig 5: 2.3L OHC MPFI Engine WOT A/C Cut-Out Circuits
G72374
  1. No A/C: Check For Voltage at A/C Clutch  - Use only DVOM, not diagnostic tester, for this step. With KOEO, set DVOM on 20-volt scale. Measure voltage between 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 system. If voltage is less than 10.5 volts, go to next step.
  2. 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 or A/C fan controller. Measure resistance between power side of A/C clutch harness connector and power-to-clutch pin at WAC relay or A/C fan controller. 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.
  3. Checking Power on A/C Demand Circuit  - With KOEO and WAC relay or fan controller disconnected, turn on A/C. Set DVOM to 20-volt scale. Measure voltage between A/C demand input pin at WAC relay or fan controller connector 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 re-test system.
  4. Checking WAC Circuit For Short to Ground  - Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector and WAC relay or A/C fan controller. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200K-ohm scale. Measure resistance between WAC circuit at relay or fan controller and chassis ground. If resistance is greater than 10K ohms, go to next step for A/C fan controller systems or step 7) for WAC relay systems. If resistance is less than 10K ohms, repair short and retest system.
  5. Checking A/C Fan Controller Ground Circuit  - With key off and A/C fan controller disconnected, set DVOM on 200-ohm scale. Disconnect ECA and measure resistance between ground circuit at A/C fan controller 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.
  6. 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 fan controller connector and 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 controller and re-test system.
  7. Checking WAC Relay or A/C Fan Controller  - Turn key off and wait 10 seconds. Leave ECA disconnected and reconnect WAC relay or fan controller. 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 re-test system. If voltage is less than 10.5 volts, replace WAC relay or fan controller. Re-test system.
  8. Checking A/C Output at WOT  - Enter OUTPUT STATE CHECK; see OUTPUT STATE CHECK  under QUICK TEST DIAGNOSTIC AIDS. Use a VOM or DVOM meter for this test. Turn key off and wait 10 seconds. Set meter on 20-volt scale. Connect meter 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 KEY ON/ENGINE OFF (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).
  9. System Identification  - If vehicle is equipped with WAC relay, go to step 12). If vehicle is equipped with A/C fan controller, go to step 14).
    • WAC Relay: 3.8L MPFI (RWD) 5.0L SEFI 5.0L MA SEFI
    • A/C Fan Controller: 1.9L CFI 1.9L MPFI 2.3L HSC MPFI 2.3L OHC MPFI
  10. 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 in VPWR circuit, remove test equipment, and re-test system.
  11. 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 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 re-test system. If voltage does not cycle, remove jumper and go to next step.
  12. Checking Continuity of WAC Circuit  - Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for 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 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.
  13. Checking For Short to Power  - Turn key off and wait 10 seconds. 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. 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 re-test system.
  14. Checking WAC Cycle  - With vehicle in OUTPUT STATE CHECK, disconnect A/C fan controller and set DVOM on 20-volt scale. Connect positive test lead to ignition run circuit and negative test lead to WAC circuit at fan controller harness connector. Check DVOM while depressing and releasing throttle several times, to cycle system. If voltage cycles from high to low, replace fan controller and re-test system. If voltage does not cycle, remove jumper and go to next step.
  15. Checking Continuity of WAC Circuit  - Turn key off and wait 10 seconds. 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 fan controller 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.
  16. Checking For Short to Power  - Turn key off and wait 10 seconds. Install breakout box, ECA and 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 fan controller and re-test system. If any reading is 10K ohms or less, repair short to power and repeat QUICK TEST  . If symptom is still present, replace ECA.
  17. Cycle A/C Demand Switch  - Turn key off and wait 10 seconds. Install breakout box, leaving ECA disconnected. Set DVOM on 20-volt scale. With KOEO, connect DVOM positive test lead to Test Pin No. 24 (No. 43 on 2.3L HSC MPFI) and negative test lead to Test Pin No. 40. If voltage goes high and low as switch is cycled, replace ECA and retest system. If voltage does not cycle, go to next step.
  18. Checking Continuity of A/C Demand Circuit  - Turn key off and wait 10 seconds. Set DVOM on 200-ohm scale. Measure resistance between Test Pin No. 24 (No. 43 on 2.3L HSC MPFI) 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.
  19. Checking A/C Demand Circuit For Short to Power  - Disconnect WAC relay or A/C fan controller. Disconnect ECA and install breakout box. With A/C demand 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 re-test system.
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