Control System Testing

1982 Buick Regal Sport, Trans Mfr CD 350C/MX5SECTION Control System Testing
  • 65° selection drives system to maximum cold.
  • 85° selection drives system to maximum heat.
  • A mode L.E.D. will flash if mode is malfunctioning. (ETCC system only)
  • A temperature L.E.D. will flash if temperature control actuator malfunctions. (ETCC system only)
  • A disconnected mode door actuator wire will cause mode L.E.D.'s to flash. (ETCC system only)
  • An inoperative mode door which is stopped in a position correct for one mode will not cause L.E.D. to flash until control panel calls for actuator to move to another position. (ETCC system only)
  • Blower delay affects only heater and bi-level modes. Switch can be checked by touching 65° on control panel. Blower operation at 65° and no blower at 85° indicates a cold engine or a malfunctioning coolant temperature switch circuit. (ETCC system only)
  • Blower delay affects only heater and bi-level modes. Check timer by touching 65° on control panel. No blower operation at 65° and blower when 85° is touched indicates malfunction in blower delay timer circuit. (TCC system only)
  • Control must have a constant B+ first and then power from ignition switch to work properly.
  • An open sensor string will drive the system to maximum heat except at 65° selection.
  • A shorted sensor string circuit will drive the system to maximum cold except at 85° selection.
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • You smell fuel, burning insulation, or see smoke.
  • Brakes feel soft, pull hard to one side, or make grinding noises.
  • The engine overheats, stalls repeatedly, or misfires under load.
  • You are missing required tools, torque specs, or safe lifting equipment.
  • You are not confident in the next step or safety outcome.