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Home >> Ford >> 1978 >> Fiesta >> Repair and Diagnosis >> Engine Mechanical >> Auxiliary Emission Control Systems >> THERMACTOR I System >> Operation >> Cold Engine Lock-Out/Overheat Protection (1975-76 Models) >> System 1: Normally Closed

System 1: Normally Closed

  1. When engine is operating at normal temperature, battery current goes through air cleaner mounted temperature sensor to solenoid vacuum valve. Some models also include a floor mounted overheat sensor.
  2. If normally closed switch(s) open (due to cold air temperature or overheated floor pan), solenoid vacuum valve will operate. This causes by-pass valve to dump thermactor air to atmosphere.
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