My friend Todd told me about this secret many years ago. He has rebuilt more cars in his suburban home garage than anyone I know.
I met Todd at my first part time job, we used to work early weekend mornings during high school. I was too young to have a driver’s license, so my dedicated parents would always drive me.
That was before remote starters, so I would usually start the car a few minutes before leaving. Actually, that’s not true — my Dad was usually the one starting the car a few minutes before I was ready to leave, which was about 10 minutes after I told him I would be ready to leave.
It didn’t make much difference to the car — it was still cold for at least half the trip. On the rare occasion that I started the car, I would turn the heater to its hottest setting and turn the fan to full blast. That’s actually the slowest way to warm the car, so lets talk more about the fastest way.
The trick is very counter-intuitive, so I want to briefly explain how the car heater works for this secret to make sense.
The item pictured above is a heater core. Most cars have one of these inside the dashboard. Hot liquid passes through the fins, which are there to create a lot of surface area so that air passing through can pickup as much heat as possible before it comes out the air vents. It works just like the radiators in many older homes in that sense.
The liquid is heated by excess engine heat, so if the engine is cold then you won’t get any hot air from your air vents. Your engine has a cooling system which is designed to draw heat away from the engine so it does not overheat. The heater works in a similar way, removing heat from the engine and using it to heat the air being blown into the passenger compartment. So, when you turn on your heater, you are essentially cooling the engine by transferring some of its heat to the inside of the car.
To heat the engine faster, you want to stop that heat loss. It’s similar to heating your oven, you don’t leave the door open because you’ll lose all of the heat.
You want to turn the heater off by moving the temperature control all the way to cold. Also, turn the fan off to ensure it is not blowing air across the heater core which transfers heat away from it. This will trap the heat in the engine cooling system (reducing its ability to cool the engine) and therefore heat the engine more quickly. It traps the heat in, just like closing the oven door.
If your car has an automatic climate control system that allows you to dial in the temperature then there is no need to worry about these suggestions to make them heat the car faster, most of these cars do it automatically. If your car has automatic climate control, it’s normal that the fan doesn’t blow when you first start the cold car. The vehicle engineers already know this secret and have programmed it into the car. The fan does not run until there is adequate engine heat to warm the air (unless you want to warm the car more slowly and manually activate the fan).
This knowledge is helpful to all drivers, even if you never plan to drive in cold weather. If your engine is overheating in hot weather, set the climate control to hot, turn the fan on full blast and roll down all the windows. This will dissipate engine heat through the heater core and help cool the engine.
