Car heater controls can look complex, but not to worry, 5 minutes from now, you’ll be an expert.
Using the car heater is a simple 3-step process:
- Engine on
- Set the desired temperature
- Turn on the fan speed
An effective heater is essential for visibility. Some manufacturers make heater controls look so intimidating; using the controls is easy, but finding the right one is the problem.
In this post, I’ll show you how to identify all the controls and explain simply what they do, why, and when you’d use them.
How To Use A Car Heater – Short Version
This is the shortened version, cos I’m guessing you’re in your car right now, freezing your knacks off. Operating a car heater is a simple three-step process. If your car is modern, it may only require the pressing of one button; either way, you’ll soon see how easy it is.
Modern cars have pretty sophisticated heating systems, called climate control systems or HVAC (Heating, Ventilation, Air Conditioning). If you own a car that’s only a few years old, look out for the Windshield Demist button on your heater console.
Pressing Demist will cause the heater control module (computer) to take control of the heating, it will clear the windshield and side windows as a priority.
Start your engine and have it idling, driving your car will help speed up the warm-up process. A car heater won’t actually blow heat until the engine warms up a little; modern cars warm up in about 5 minutes.
The time it takes to warm up will depend mostly on how cold it is outside, and you’ll find older cars, cars with big engines, and diesel engines will take the most amount of time.
Locate and adjust the temperature control button. Some vehicles will have a simple toggle wheel; others will have a digital display. Typically measured in degrees C from low – to high 28°.
Higher-end cars will have dual climate controls; it’s a fancy word for two temperature control knobs – one for the driver side and another for the passenger side. For full heat, move both controls to the maximum setting.
Turn on the heating system by simply turning on the fan. Adjust the blower motor to your desired speed. Note your heater may be different; it may not have a knob, but it could instead be a button. Either way, it will have the fan symbol, that’s basically the “On” button.
The blower motor is a fan that has various speed settings. Turning the fan speed to high doesn’t adjust the temperature; it simply increases the distribution of whatever heat is available or pre-selected.
That’s it; that’s enough knowledge to get the heat in your car going. Your car’s heater is a clever bit of kit, and it’s got some really useful buttons that make driving a lot more comfortable; you can check them out below.
What Do The Different Heater Controls Do?
Here we’ll look at each of the heater controls in more detail, how to identify them, what they do, and when you’d actually use them.
You already know how to turn on the car heater and adjust the heat, but a modern car heater is a very sophisticated kit, so sophisticated they don’t call them heaters anymore. They call the climate control systems.
Climate control systems are managed by their own dedicated control unit (computer). The heater controls are grouped together on a panel and positioned in the center console.
The climate control unit is connected to other control units in the car; they all play a part in-cabin climate management.
You’ll notice the engine management control unit helping out when you set the heater fan to high; the engine revs will often rise. The climate system also manages the a/c system and can take account of the sun load hitting the car.
Knowing what all these buttons do will help you manage any in-car climate situation, from frozen toes to extreme sun and even unpleasant exterior odors.
The temperature control button is obviously crucial to an effective in-car heating system. We’ve all been in a car when it’s too hot or cold; it’s not a comfortable experience.
Finding the sweet spot will require adjustment, especially as your body temp changes; that’s why the temperature control buttons are probably the most important and heavily used on your heating control panel.
Heating controls on modern cars usually incorporate a digital display and two buttons, one for higher and the other for lower. Older vehicles may use a colored toggle wheel; it’s effective and gives a great visual cue as to what it controls, blue for cool and red for warm.
Many vehicles will have dual temp controls, one to adjust the driver’s zone and a second for the front passenger zone. Some may even have a rear passenger temperature control zone.
What’s Blower Motor?
Without the blower (fan), the hot air won’t move around the car or clear the windshield. The fan button is effectively the “on button” for the whole heating system.
The blower has various speed settings, and as you already know, a higher speed doesn’t mean higher temperatures; it simply moves the air more quickly.
Like the temp control on modern cars, the fan control also usually incorporates a digital display and two buttons, one for higher speeds, the other lower, but a simple twist knob is also common.
What’s Air Distribution?
The ability to direct air is extremely important, especially on a frosty morning, a rainy day, or dead heat. Heater air can be directed using the control panel controls. The most common and important directions include:
- Side windows of car
- Feet of passengers
- Face of passengers
- Feet and face
Air can be further directed by manually adjusting the airflow vents mounted in the dashboard. The air is directed by controlling blend doors inside the heater box, and since computers are now in charge of climate controls, the direction options are ever-increasing.
Air direction control in modern cars is usually a digital graphic of a seated person; a single button that scrolls around a set menu is also pretty standard. Older vehicles may have a button that is identified by a graphic indicating its function.
What’s Windshield Demist?
Modern climate systems will have a demister button; some models may call by a different name, such as the defroster. It’s a single button, and its function is to clear the windshield and side windows in the shortest possible time without you having to fiddle with any other controls.
It’s a pre-programmed setting and utilizes the a/c system to dehumidify the air. This is the correct setting for a frosty or fogged-up windshield; however, the demist setting should be shut off after it clears.
You’ll often find a delay between pressing the button and action because the heater hasn’t got sufficient heat from the engine yet.
What’s The Auto Setting For?
The auto setting regulates whatever temperature the temp is set to. Some climate systems may call it by a different name, such as comfort mode.
The auto button will automatically control the a/c, fan, and other settings to reach and maintain the car’s interior at whatever temperature you have pre-selected. This is the perfect setting for everyday use, simply set the temperature and hit auto.
What’s Recirculation Button Do?
A car heater normally uses outside air to heat the cabin. It pulls air from an outside air vent through a cabin filter to catch any bugs or dust, then through the heat exchanger. The now heated air is distributed to car interior air vents.
So what’s a recirculate button, and why would you use it?
The re-circulation button prevents outside air from entering the cabin. Since a car takes a while to heat up on cold starts, recirculating the partially heated cabin air is the most efficient and fastest way to get the cabin to the desired temperature.
The same is true for cooling a cabin; the a/c will cool more quickly since it’s cooling already-cooled air.
The recirculate button is also useful for short periods when the outside air is poor, say in traffic behind a smelly diesel. Although using it for prolonged periods will cause the windows to mist over and the cabin air quality to deteriorate.
Two recirculation symbols are common, a circular symbol with arrows for modern cars and a car with an inward direction arrow symbol for older cars.
Rear Heated Window
The rear heated window is excellent in the frosty weather; turning on the switch creates heat in the rear window glass. Although not technically a climate control button, the rear heated window is usually grouped with them.
The rear heated window is a heavy power consumer and is wired to auto-turn off. A workshop repair manual covers every aspect of car operation, maintenance, and repair, including troubleshooting sections; for a few dollars, they contain a ton of useful info.
Do you turn on a/c for heat in a car? Turn on a/c is for cold air and also to help demist the windshield. To turn on the heat, move temperature knobs to full and turn on the fan.
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John Cunningham is an Automotive Technician and writer on Rustyautos.com. He’s been a mechanic for over twenty-five years and has worked for GM, Volvo, Volkswagen, Land Rover, and Jaguar dealerships.
John uses his know-how and experience to write fluff-free articles that help fellow gearheads with all aspects of vehicle ownership, including maintenance, repair, and troubleshooting.