Mike's Workshop Manuals: Service manuals for every vehicle
Home >> Pontiac >> 1971 >> GTO Base, 6.6L Eng, Eng CD WS, Automatic Trans >> Repair and Diagnosis >> Heating, Ventilation & A/C (HVAC) >> HVAC Control Systems >> Automatic Temperature Control >> Adjustment >> Feedback Potentiometer (Programmer Amplifier) Calibration

Feedback Potentiometer (Programmer Amplifier) Calibration

  1. Remove programmer cover (do not disturb programmer mounting or link connection). Connect ATC Tester J-23678 into wiring harness and programmer. Place control head selector lever in "AUTO" position and set temperature dial at "75".
  2. Insert blade type screwdriver in slotted adjusting screw in center of feedback potentiometer gear and slip the potentiometer shaft fully counterclockwise to its stop (gear will not turn). Vacuum motor should be in full heat position with stem moved fully in toward motor.
  3. Place tester "Manual Automatic" switch in "Manual" position and rotate tester "Manual Control" knob to "Max. Heat" position, then rotate knob to exactly 180 and STOP in this position
    CAUTION: (Do not over-travel or back knob up).
  4. With screwdriver engaging potentiometer adjusting screw, turn screwdriver very slowly to slip potentiometer shaft in a clockwise direction until first movement of vacuum motor mechanism is noted (do not watch output shaft and do not turn screwdriver beyond point where movement first starts).
  5. To check above adjustment, rotate tester "Manual Control" knob to "Max. Heat" position, then slowly rotate knob back toward "180". Vacuum motor mechanism should first start to move when knob indicates 180 ± 1. Touch up the potentiometer adjustment as necessary so that this movement occurs at exactly 180. If this adjustment cannot be made, programmer is defective.
    Fig 1: Feedback Potentiometer Adjustment
    G09311437Courtesy of GENERAL MOTORS COMPANY
scientia non olet · About Mike's Workshop Manuals