The cabin heating system uses heated coolant from the engine to produce warm air for the passenger compartment. This simple system has been used on cars and trucks for many years and continues to be a reliable way to warm the cabin of late-model vehicles.
Heater Core
The heater core is a small heat exchanger that looks similar to the radiator that is located in the front of the vehicle. The heater core is located in the duct box and it receives heated coolant from the engine. The materials used to manufacture heater cores include copper, aluminum, and plastic. Hoses and pipes are connected to the heater core to supply heated coolant to the device.
Coolant Flow Valve
Some manufacturers use a coolant flow valve that controls the flow of heated coolant into the heater core. This valve is located in series with the heater hoses or coolant pipes and is typically controlled with a cable or vacuum valve. The valve opens and closes by moving the heater control lever on the control panel. Not all cars and trucks will have one of these valves, because most systems use a door to control the temperature of the air that is distributed to the passenger compartment.
The heater core is the heat exchanger located in the duct box that provides the warm air for the passenger compartment. This heater core is made from aluminum and has plastic tanks as well as plastic
This heater core is made from aluminum with the end cap made from plastic. The pipes for this heater core are bolted on and are made from aluminum like the
The coolant flow valve controls the flow of coolant into the heater core mechanically with a lever that is activated by a cable that connects to the temperature-control knob on the control head. This valve is made from plastic and has metallic levers that bolt to the
This heater control valve is controlled with a vacuum signal from the control head. The valve is open when the temperature lever is moved to the heat position and it closes when the temperature lever is moved to the cool position. The valve can be tested by using a vacuum pump connected to the vacuum port. The valve will hold a vacuum seal for at least a minute if it is
This heater control valve is electrically actuated with a signal that is received from the control head. This unit uses a solenoid that opens and closes the passage as the temperature knob is moved from hot to
This heater control valve is electrically actuated with a signal that is
received from the control
Hoses and Pipes
As explained before, hoses and pipes are needed to connect the engine cooling system to the heating system components. These hoses and pipes simply provide a pathway for the heated coolant to reach the heater core.
Blend Door
All vehicles use a blend air technique to control the temperature of the air that is distributed into the passenger compartment. This system was described in more detail in chapter The main device that controls the temperature of the air is the temperature door, which is also known as the blend door. The blend door acts to control the temperature of the air by controlling the flow of the air through or around the heater core.
When the blend door is in the full-heat position, all of the duct box air passes through the heater core, which heats the air to maximum temperature. When the blend door is in the full-cool position, all of the duct box air bypasses the heater core, which prevents the air from being heated by the heater core. If the blend door is at any point between full hot and full cool, the air is blended because some to the air will pass over the heater core and some of the air will bypass the heater core.