How It Works: Your Car's Heating System

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When the weather turns cold, few things on your vehicle seem as important as its heater. Its controls may be on the dash, but the heart of how most of them work begins inside the engine with its cooling system.

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Regular maintenance on that system not only benefits the engine, but can keep your vehicle’s heater in good condition as well.

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An engine generates so much heat from combustion and friction that if it isn’t continuously cooled, it can suffer serious damage. Virtually all modern vehicle engines are liquid-cooled, using water blended with antifreeze to reduce corrosion and keep it from freezing.

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The coolant is pumped through channels in the engine, called water jackets, where it absorbs heat. It then travels into the radiator where it cools down before going back into the engine in a continuous loop.

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The clogged tubes in this heater core prevented coolant from circulating properly, and the climate system only blew out cold air.
The clogged tubes in this heater core prevented coolant from circulating properly, and the climate system only blew out cold air. Photo by Jil McIntosh /Driving
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Some of the hot coolant makes a detour from the engine through a water valve and over to the heater core. This is a miniature version of the radiator, with tubes for coolant circulation and cooling fins to dissipate the heat.

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When you turn on the fan, a blower motor sends the air warmed by the heater core into the cabin. To regulate the temperature, small “blend doors” open or close to regulate how much hot or cold air enters the cabin from the heater core or air conditioning unit. There’s also a flap that regulates how much fresh air comes into the climate system from outside.

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Setting the system to “Recirculate” closes this outside flap, and the climate system receives only inside air to be heated or cooled. This helps it to reach the desired temperature quickly, and can also prevent outside odours from getting in (flip it closed quickly when you see the dead skunk up ahead!), but leaving it in that position too long can build up condensation and cause the windows to steam up. If too little fresh air comes in, it can also create higher carbon dioxide levels, which can make you drowsy.

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Some automatic systems allow for rear passengers to adjust their climate settings.
Some automatic systems allow for rear passengers to adjust their climate settings. Photo by Jil McIntosh /Driving
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If your vehicle has automatic climate control, it uses sensors to monitor the cabin, and then opens or closes the blend doors and outside flap as needed to maintain the temperature you’ve set. Dual-zone systems, which allow driver and passenger to set different temperatures, operate individual blend doors on either side of the dash.

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    CIBC logoTD logoIA logoRBC logoScotia Bank logoPre-qualify todayPowered by Jil McIntosh picture

    Jil McIntosh

    Jil McIntosh specializes in new-car reviews, auto technology and antique cars, including the two 1940s vehicles in her garage. She is currently a freelance Writer at Driving.ca since 2016

    Summary

    · Professional writer for more than 35 years, appearing in some of the top publications in Canada and the U.S.

    · Specialties include new-vehicle reviews, old cars and automotive history, automotive news, and “How It Works” columns that explain vehicle features and technology

    · Member of the Automobile Journalists Association of Canada (AJAC) since 2003; voting member for AJAC Canadian Car of the Year Awards; juror on the Women’s World Car of the Year Awards

    Education

    Jil McIntosh graduated from East York Collegiate in Toronto, and then continued her education at the School of Hard Knocks. Her early jobs including driving a taxi in Toronto; and warranty administration in a new-vehicle dealership, where she also held information classes for customers, explaining the inner mechanical workings of vehicles and their features.

    Experience

    Jil McIntosh is a freelance writer who has been writing for Driving.ca since 2016, but she’s been a professional writer starting when most cars still had carburetors. At the age of eleven, she had a story published in the defunct Toronto Telegram newspaper, for which she was paid $25; given the short length of the story and the dollar’s buying power at the time, that might have been the relatively best-paid piece she’s ever written.

    An old-car enthusiast who owns a 1947 Cadillac and 1949 Studebaker truck, she began her writing career crafting stories for antique-car and hot-rod car club magazines. When the Ontario-based newspaper Old Autos started up in 1987, dedicated to the antique-car hobby, she became a columnist starting with its second issue; the newspaper is still around and she still writes for it. Not long after the Toronto Star launched its Wheels section in 1986 – the first Canadian newspaper to include an auto section – she became one of its regular writers. She started out writing feature stories, and then added “new-vehicle reviewer” to her resume in 1999. She stayed with Wheels, in print and later digital as well, until the publication made a cost-cutting decision to shed its freelance writers. She joined Driving.ca the very next day.

    In addition to Driving.ca, she writes for industry-focused publications, including Automotive News Canada and Autosphere. Over the years, her automotive work also appeared in such publications as Cars & Parts, Street Rodder, Canadian Hot Rods, AutoTrader, Sharp, Taxi News, Maclean’s, The Chicago Tribune, Forbes Wheels, Canadian Driver, Sympatico Autos, and Reader’s Digest. Her non-automotive work, covering such topics as travel, food and drink, rural living, fountain pen collecting, and celebrity interviews, has appeared in publications including Harrowsmith, Where New Orleans, Pen World, The Book for Men, Rural Delivery, and Gambit.

    Major awards won by the author

    2016 AJAC Journalist of the Year; Car Care Canada / CAA Safety Journalism award winner in 2008, 2010, 2012 and 2013, runner-up in 2021; Pirelli Photography Award 2015; Environmental Journalism Award 2019; Technical Writing Award 2020; Vehicle Testing Review award 2020, runner-up in 2022; Feature Story award winner 2020; inducted into the Street Rodding Hall of Fame in 1994.

    Contact info

    Email: [email protected]

    Linkedin: https://www.linkedin.com/in/jilmcintosh/

    Twitter: https://twitter.com/JilMcIntosh

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Tag » How Does Heater Work In Car