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Home › Plymouth › 1978 › Arrow Base, Automatic Trans › Repair and Diagnosis (Single Page) › Heating, Ventilation & A/C (HVAC) › HVAC Control Systems › Auto. A/C Systems › Testing › System Calibration Test › Amplifier Check

Amplifier Check

Before making this test, allow system to warmup for 15 minutes with system on, in Heat mode, and tester Mode Knob at "Heat". Test amplifier as follows:

  1. Turn tester mode knob to "MID" and when voltage on voltmeter drops to zero, disconnect inboard electrical insulator (6-way) at servo assembly.
  2. Using an accurate ohmmeter, check resistance across the black and violet wires (see Figure). Resistance should be between 1000 and 1200 ohms. If resistance is not within tolerance, replace amplifier.
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