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MTC Test 1A: EBL (Defogger) Switch Failure

  1. Place A/C mode switch in RECIRC/BI-LEVEL (full left) position. Using scan tool, erase DTCs, then select SENSORS. Monitor MODE SWITCH MUX voltage. If voltage displayed is about .2 volt, go to next step. If voltage displayed is not about .2 volt, go to step  4 .
  2. Using scan tool, monitor MODE SWITCH MUX voltage. Disconnect A/C-heater control head 12-pin connector. If voltage rises to 5 volts, replace A/C-heater control head. If voltage does not rise to 5 volts, go to next step.
  3. Ensure ignition is off. Disconnect Body Control Module (BCM) Black connector. BCM is mounted to junction block located behind left end cap of instrument panel. Using an external ohmmeter, measure resistance between ground and BCM Black connector terminal No. 22 (Red/Tan wire). See Fig 1 . If resistance is less than 100 ohms, repair Red/Tan wire for short to ground. If resistance is 100 ohms or more, replace BCM.
    Fig 1: Identifying Body Control Module Black Connector Terminals
    G98E00097Courtesy of CHRYSLER CORP.
  4. Press and release rear defogger button several times. If button intermittently sticks, replace A/C-heater control head. If button does not stick intermittently, go to next step.
  5. Using scan tool, monitor MODE SWITCH MUX voltage. If voltage displayed is about 4.3 volts with defogger button released, replace A/C-heater control head. If voltage displayed is not about 4.3 volts with defogger button released, go to next step.
  6. Press and hold control switch. Monitor MODE SWITCH MUX voltage. If voltage displayed is about .4 volt, defogger system is currently operating correctly. If voltage displayed is not about .4 volt, replace A/C-heater control head.
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