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Home › Ford › 1979 › Fiesta › Repair and Diagnosis › Engine Mechanical › Auxiliary Emission Control Systems › THERMACTOR I System › Testing › COLD ENGINE LOCK-OUT/OVERHEAT PROTECTION (1975-76 Models) › Normally Open System Two

Normally Open System Two

  1. Warm engine to normal operating temperature. Ambient temperature should be about 65°F. Disconnect vacuum hose at air by-pass valve.
  2. Air by-pass valve should dump air to atmosphere. If it does not, vacuum supply is not operating correctly. Reconnect hose.
    NOTE: Vacuum supply always goes to Black fitting on solenoid valve.
  3. Disconnect wires from solenoid and then reconnect hot wire only. If by-pass valve DOES NOT dump air, when other exposed terminal is grounded, solenoid valve is defective. If by-pass valve dumps air when wires are reconnected, check temperature switch in air cleaner.
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