Spark

Thermostat Heater Control System Description

A conventional thermostat valve is moved only by the coolant temperature. The temperature range at which the thermostat begins to open is fixed and cannot be adjusted. An electric thermostat valve is moved by the coolant temperature and the built-in heater that is controlled electrically by the ECM. The ECM controls the heater by providing a pulse width modulated (PWM) ground to the thermostat heater control circuit. In this system, a desired ECT can be achieved causing the vehicle better fuel consumption and reduced emissions in city driving or slow cruising.