Early Fuel Evaporation System: Operation
When ignition switch is in the "ON" position, voltage is applied to a thermoswitch located in intake manifold. If engine coolant temperature is less than a calibrated value, the thermoswitch completes the circuit to the heater, and allows 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 will reduce the temperature to less than regulated value. When coolant temperature reaches calibrated value, thermoswitch turns off and current to heater is cut off.