Combustion engines have an operating temperature between 180 and 220 degrees Fahrenheit, which makes them an ideal place to draw warmth for drivers and passengers.
While many folks may not give a lot of thought to what happens when they push or turn their dashboards’ touchscreens or dials (respectively), there is plenty going on under the hood.
Here is a Car 101 look at your car heater.
Common pieces of a car heater in vehicles with combustion engines include the following: a heater core, a blower, a heater hose, control valves and dashboard controls. All of these parts are located under the hood, in the engine or in the passenger compartment.
How’s does my car heater work?
Warm air entering your vehicle starts its trip to your dashboard, your feet or your face through ducts on your vehicle’s hood or grill. When a vehicle is moving, air flows through these openings toward a heater core – sometimes known as a heater matrix – that resembles a small radiator. If your vehicle is stationary, air is blown onto the heater core by a fan.
Vehicle heater cores are commonly located inside the passenger compartment, behind the dashboard.
The heater core is warmed by a mixture of water and engine coolant pushed through the engine by a water pump. The mixture takes heat from the engine and, through a series of hoses and tubes, carries this heat through the heater core.
It can take several minutes or more for a vehicle’s engine to warm up to a point where the coolant mixture can carry heat to the heater core. That’s why, on colder days, you aren’t able to get in, turn on your car and immediately enjoy warm air from your car heater.
A blower pushes air over the heater core toward the passenger compartment. The core has several ducts that direct air to different areas of the vehicle, such as floor vents, dashboard vents and the defroster. The opening and closing of these ducts was traditionally handled by cable or vacuum systems, though newer models use computer-controlled motors.
How is the temperature managed?
In most modern vehicles with automatic climate control, the heater temperature is controlled by a sensor that triggers the opening and closing of flaps. These flaps allow outside air to reach the core. The cooler the desired temperature, as dictated by the dashboard controls, the more air flows onto the core. The warmer the desire temperature, the less air flows onto the core. On a conventional system with knobs, the driver adjusts the temperature.
So, if my vehicle isn’t blowing hot air, is my car heater broken?
There are several situations that could lead a vehicle’s heating system to malfunction. You could be leaking engine coolant. Your thermostat, which dictates the flow of coolant through the engine, may be stuck, preventing coolant from picking up the heat it needs to warm the heater core. Your dashboard controls could be broken or the fan may not be blowing warm air or even the cabin air filter if equipped could be hampering air flow.
What is the ideal time to let my vehicle’s engine warm up?
You don’t need to let your vehicle warm up for a particularly long period. A minute or so is enough, so long as you take it easy for the first few miles.
If you want heat as soon as you pull away, however, you’ll likely want to let your vehicle warm up until your dashboard temperature gauge starts to climb toward its normal operation level.
What about vehicles without water pumps?
In vehicles with air-cooled engines, a water pump and coolant mixture are replaced with a circulation system that sends air directly over warm parts of the engine. Since there is no coolant mixture to send through the heater core, there is no heater core. Most of the heat from an air-cooled engine is passed back out in the air by a series of fins, though some can be directed into the passenger compartment with a blower.
How do I know if my vehicle is water- or air-cooled?
If your car has an engine, it is almost certainly water-cooled.
What about cars that don’t have engines?
Electric vehicles use electricity to provide passenger compartment heat, often at the expense of range.
Electric vehicles are already compromised by cold weather. A 2014 AAA test found that vehicles with an average range of 105 miles at 75 degrees Fahrenheit experienced a 57 percent drop, to 43 miles, when temperatures held steady at 20 degrees Fahrenheit.
Using battery power to heat the passenger compartment has the potential to reduce this range further. It’s why manufacturers such as Chevrolet put out cold weather tips such as this, advising Volt owners to heat the cabin of their vehicles while still plugged in to chargers, or use heated seats.
Manufacturers are looking to ease the impact of heating systems on range, as evidence by Nissan. The Leaf uses a heat-pump cabin heater that is said to use less power than conventional electric vehicle heating systems.
It’s kind of complicated, so here it is straight from the manufacturer:
“When the heater is in use, [an] external capacitor absorbs heat from the atmosphere and then compresses it into high-temperature heat. The cold air in the cabin is heated and hot air is blown into the cabin out of the air-conditioning grille. After the heat decompresses to a low temperature, it is released out of the car.”
You can check out a nifty graphic of this process here.
To learn more about car parts and how they work, visit AAA.com/Car101.
Written with contribution from AAA’s Car Doctor, John Paul.