Heating System

With the Ignition switch in RUN, voltage is present at the Heater Control Assembly Blower Switch through the HEATER Circuit Breaker, the Blower Motor winding and the Blower Motor Resistors.

With the Blower Switch in any position but OFF, current flows through the HEATER Circuit Breaker, the Blower Motor winding, the Blower Motor Resistors and the Blower Switch to ground. The Blower Motor runs at speed "1," "2," "3," or "4," depending on Blower Switch position. In position "1," current must pass through three dropping resistors, so the blower motor runs at a slow speed. In position "2," current passes through two dropping resistors and the blower motor runs faster. In position "3," current passes through only one dropping resistor, so the blower motor runs still faster. In position "4," current bypasses all three dropping resistors, so the blower motor runs at the fastest speed.

Vehicles equipped with the Blower Switch in any position but OFF, a "blower on" input is provided to pin S of the EGI Control Module.