Heating

The purpose of the heater is to supply heat to the interior of the vehicle. The vehicle operator can determine the level of heat by turning the temperature control, located on the HVAC control module, to any setting. The temperature control can change the vehicle's air temperature regardless of the HVAC mode setting, heater or A/C.

The instrument panel fuse block provides power to the air temperature actuator through the ignition 3 voltage circuit. Power and ground are provided to the HVAC control module by the ignition 3 voltage, battery positive voltage, ground circuits and splice pack. A battery positive voltage is sent out over the ignition 3 voltage circuit to the air temperature actuator. When a desired temperature setting is selected, a variable resistor is used to determine the air temperature actuators setting. The resistor is located within the HVAC control module. That varied 12-volt signal is sent to the logic circuit inside the air temperature actuator on the air temperature door control circuit. The motor opens the air temperature door to a position to divert sufficient air past the heater core to achieve the desired vehicle temperature. The air temperature actuator is grounded through the ground circuit and splice pack.

Engine Coolant
Engine coolant is the key element of the heating system. The normal engine operating coolant temperature is controlled by the thermostat. The thermostat also creates a restriction for the cooling system that promotes a positive coolant flow and helps prevent cavitation.

Coolant enters the heater core through the inlet heater hose, in a pressurized state. The heater core is located inside the HVAC module. The heat of the coolant flowing through the heater core is absorbed by the ambient air drawn through the HVAC module. Heated air is distributed to the passenger compartment, through the HVAC module, for passenger comfort. The amount of heat delivered to the passenger compartment is controlled by opening or closing the HVAC module temperature door. The coolant exits the heater core through the return heater hose and recirculated back through the engine cooling system.