Early Fuel Evaporation System: Operation
When ignition switch is turned to the "ON" position, voltage is applied to a thermo switch located in intake manifold. If engine coolant temperature is below a calibrated value, the thermo switch is in an "ON" condition and a circuit is completed to the heater, allowing current to flow.
The heater, incorporating a positive temperature coefficient semiconductor element, increases in temperature and then self-regulates at a calibrated temperature. This is in effect except at high engine speeds when air/fuel flow will reduce the temperature below regulated value. When coolant temperature reaches calibrated value, thermo switch turns off and current to heater is cut off.