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Home › Cadillac › 1969 › Calais Not Available, Automatic Trans › Repair and Diagnosis › Heating, Ventilation & A/C (HVAC) › HVAC Control Systems › Automatic Temperature Control - Rear Unit › Testing The FLEETWOOD Rear System › (B) Sensor String Test

(B) Sensor String Test

  1. With engine not running connect Control Tester J-21512, set rear unit temperature dial to 71°, and start engine.
  2. Place Amplifier switch on Tester in SENSOR position and the Sensor switch to A/C position. System and Tester meter should go to full A/C.
  3. Place Sensor switch in HTR position and the system and Tester meter should go to full heater.
  4. If system responded OK to sensor tests disconnect Control Tester and reconnect car wiring harness. Inspect all three sensors (in-car, duct, and ambient) for loose or defective connectors, Repair or replace if needed.
  5. Using an ohmmeter check resistance values of the three sensors against values shown on Resistance Graph of Sensors. If ohmmeter is not available new sensors may be substituted, one at a time, testing for proper system operation after each substitution.
  6. If system still does not operate properly reconnect Tester J-21512 and perform TEST (C).
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