Car & Truck Heating Systems/Heater Core

It’s getting near that time of year again when we will need the car or truck heater instead of the air condition. So is yours working, was it working properly last season? If your heating system gave you any trouble last season and you didn’t tend to it now’s the time. Things don’t fix themselves, and when it gets worse it gets worse. If the heater core goes it could empty coolant all over the floor of the interior of your car so don’t wait for that to happen. Here’s some information on how the heating system works in an automobile, so you will be a more educated customer if and when you need assistance with your heating system.

A heater core is a radiator-like device used in heating the cabin of a vehicle. Hot coolant from the vehicle's engine is passed through a winding tube of the core, a heat exchanger between coolant and cabin air. Fins attached to the core tubes serve to increase the surface for heat transfer to air that is forced past them, by a fan, thereby heating the passenger compartment.

The internal combustion engine in most cars and trucks is cooled by a water and antifreeze mixture that is circulated through the engine and radiator by a water pump to enable the radiator to give off engine heat to the atmosphere. Some of that water can be diverted through the heater core to give some engine heat to the cabin or adjust the temperature of the conditioned air.

A heater core is a small radiator located under the dashboard of the vehicle, and it consists of conductive aluminum or brass tubing with cooling fins to increase surface area. Hot coolant passing through the heater core gives off the heat before returning to the engine cooling circuit.

The squirrel cage fan of the vehicle's ventilation system forces air through the heater core to transfer heat from the coolant to the cabin air, which is directed into the vehicle through vents at various points.

Once the engine has warmed up, the coolant is kept at a more or less constant temperature by the thermostat. The temperature of the air entering the vehicle's interior can be controlled by using a valve limiting the amount of coolant that goes through the heater core. Another method is blocking off the heater core with a door, directing part (or all) of the incoming air around the heater core completely, so it does not get heated (or reheated if the air conditioning compressor is active). Some cars use a combination of these systems.

Simpler systems allow the driver to control the valve or door directly (usually by means of a rotary knob, or a lever). More complicated systems use a combination of electromechanical actuators and thermistors to control the valve or doors to deliver air at a precise temperature value selected by the user.

Cars with dual climate function (allowing driver and passenger to each set a different temperature) may use a heater core split in two, where different amounts of coolant flow through the heater core on either side to obtain the desired heating.

The heater core is made up of small piping that has numerous bends. Clogging of the piping may occur if the coolant system is not flushed or if the coolant is not changed regularly. If clogging occurs the heater core will not work properly. If coolant flow is restricted, heating capacity will be reduced or even lost altogether if the heater core becomes blocked. Control valves may also clog or get stuck. Where a blend door is used instead of a control valve as a method of controlling the air's heating amount, the door itself or its control mechanism can become stuck due to thermal expansion. If the climate control unit is automatic, actuators can also fail.

Another possible problem is a leak in one of the connections to the heater core. This may first be noticeable by smell (ethylene glycol is widely used as a coolant and has a sweet smell); it may also cause (somewhat greasy) fogging of the windshield above the windshield heater vent. Glycol may also leak directly into the car, causing wet upholstery or carpeting.

Electrolysis can cause excessive corrosion leading to the heater core rupturing. Coolant will spray directly into the passenger compartment followed by white colored smoke, a significant driving hazard.

Because the heater core is usually located under the dashboard inside of the vehicle and is enclosed in the ventilation system's ducting, servicing it often requires disassembling a large part of the dashboard, which can be labor-intensive and therefore expensive.

Since the heater core relies on the coolant's heat to warm the cabin air up, it obviously won't begin working until the engine's coolant warms up enough. This problem can be resolved by equipping the vehicle with an auxiliary heating system, which can either use electricity or burn the vehicle's fuel in order to rapidly bring the engine's coolant to operating temperatures.





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