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Air Conditioning Signal

  1. Connect ECM test harness between ECM and ECM connectors. Unplug connector "C" from main harness only. DO NOT  disconnect from ECM. Turn ignition on.
  2. Measure voltage between ECM terminals C3 (positive) and A26 (negative). See Figure . If voltage is not about 10 volts, substitute a known-good ECM, and recheck voltage.
  3. If voltage is about 10 volts, reconnect connector "C" to main wiring harness. Momentarily connect terminals A15 and A26 together, and check for clicking of A/C clutch.
  4. If A/C clutch clicks, go to next step. If A/C clutch does not click, jumper Red/Blue wire of A/C clutch relay connector to ground. If A/C clutch clicks, repair open in Red/Blue wire. If A/C clutch still does not click, repair A/C clutch circuit.
  5. Start engine, and turn blower on. Turn A/C switch on. If A/C operates, A/C signal is okay. If A/C does not operate, measure voltage between terminals C3 (positive) and A26 (negative).
  6. If voltage is more than one volt, repair open in Blue/Black wire between terminal C3 and cooling fan control unit. If voltage is less than one volt, substitute a known-good ECM, and recheck voltage.
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