Is It Bad To Turn Your Car On/Off With Heater On? (Must Read)

Choosing to leave your heater on while turning your car on or off will not affect it in any negative way. 

Is it safe to allow your car to idle while the heater is on? How long should you let the car warm up before driving?

If you want to learn more about caring for your vehicle, keep reading! 

Let’s Find Out If It’s Bad To Turn Your Car On/Off With Heater On

This depends on the car type and model. For newer cars, it is not harmful to leave the heater on while turning your car on or off. The heater shuts off and turns on with the car’s engine and will not damage the vehicle at all. All that may happen is your heater will turn on without you noticing and make you hot and uncomfortable. Old cars however can put additional stress on the battery, reducing its overall life.

Car heater and front vents
Car heater and front vents

Leaving the heater on will not significantly impact your car’s performance. Turning the car on while the heater is on will not harm the car either. Modern cars do not drain the battery life while the car is shut off, and thus your car should work fine. 

Old cars have something known as a carburetor, which we will discuss in more detail later. However, these engines differ significantly from modern fuel injection engines. 

People learning to drive in the 1960s and 1970s were often taught to shut everything off before turning off the car. This wasn’t because it would hurt the car, though. It was to protect the car battery and extend its life. 

Today’s cars don’t work the same way. You can always leave your heater on and not worry about whether you’re turning it off. 


How Long Should You Let Your Car Warm Up On A Cold Start?

Car dual zone climate control
Car dual-zone climate control

It would be best if you allowed your car to run for at least one minute before driving. This will help warm up the fuel and ensure the car is adequately lubricated. However, warming the car for longer isn’t necessary since it won’t improve the engine function. 

Many warm their cars for 5-10 minutes before driving them in winter. The notion of warming the car is often drilled into our minds. But it turns out that this isn’t necessary anymore! 

Back in the 1960s, people used to have to allow their cars to warm up for 10 minutes or more on cold days. Many people fell into the habit of starting their day by switching on their vehicle, drinking their coffee, and finishing preparing for the day. 

Meanwhile, their car would heat up for their ride to work. 

However, this isn’t the case anymore. This is because we don’t usually use carburetors in our cars anymore. 

This is thanks to the introduction of fuel-injection engines. These engines utilize pumps rather than suction and pistons. This allows the engine and its respective parts to lubricate and heat up more quickly. 

Nowadays, the only reason you need to run your car for more than 30 seconds to a minute is to thaw the windshield. People may also start their cars early and allow them to run idle so the engine warms up to heat the car. 

Is It Bad To Turn Heater On When Car Is Idle?

Turning your heater on while your car idles will not harm your vehicle. However, you need to ensure your car is not inside a garage or that the tailpipe is blocked in any way. Allowing your car to idle outside is the safest way to warm your car while it idles. 

Many people believe it’s bad for the car to idle with the heat on because it might cause the car to shake. However, this shaking isn’t caused by the heater.

According to RX Mechanics, this shaking is indicative of other possibly serious issues with your car, including:

  • Broken cooling fan 
  • Dirty throttle 
  • Damaged spark plugs 
  • Misfiring pistons 

These issues can also occur when the car’s air conditioning is running. This shaking is probably occurring while you’re driving, but you may be less likely to feel it. 

Even though idling your car with the heater on isn’t bad for the car, it can be bad for you. 

Many countries prohibit idling cars from staying in one place for longer than 5-10 minutes. These laws exist for the well-being of the local environment since exhaust harms people’s health. 

There are usually exceptions for those trying to clean their windshield of ice. 

Last, idling your car with the heater on can hurt you. Never turn your car on and allow it to idle inside a garage. This could fill the room with carbon monoxide and poison you. Likewise, if you’re outside and your exhaust pipe is blocked by ice, snow, or something else, it could seriously harm you. 

Check out this great article on car heaters and potential health issues: Is Car Heater Bad For My Health? (8 Preventive Measures)

When Should You Start Turning Your Car Heater On?

You can start your car heater as soon as you like after turning on your car. Additionally, you can leave your heater on when you switch your car off. However, remember that the heater will not be warm until after the engine has warmed. 

You can’t turn your car heater on too soon. The heater fans might blow cold air on you, but since the air outside will be cold until the engine warms. 

Therefore, while it won’t hurt your car or you, it might waste your time. It will probably make you colder since the fans will pull in cold air from outside.

To avoid this, you could wait 2-5 minutes before turning on your car heater after starting your engine. This will also allow the engine to warm up faster than if the fans were blowing over it. 

Should You Shut Off Car Accessories Before Turning Off Your Car? 

It is not necessary to turn off your car accessories before shutting off your car. Modern car batteries are no longer drained by accessories left on after the car engine shuts off. The only exception is car lights which should always be shut off when you shut off your car.

Car accessories include several optional and essential features of your automobile. Some of these include the following: 

  • Radio 
  • Heater 
  • Air conditioner 
  • Windshield wipers 
  • Lights 
  • Headlights 

According to Telegram: Car Talk, old cars used to require you to shut down all car accessories. In modern cars, the battery is directly connected to the starter motor. This means when the vehicle shuts off, there’s no energy being pulled from the battery. 

Most modern cars will shut off your headlights as soon as the engine turns off. However, even the ones that don’t shut off automatically will shut down after a short period of time. 

You’ll need to ensure the windshield wipers are shut off in snowy regions. Many drivers may have noticed that if you leave your windshield wipers on, they’ll start moving as soon as you turn the key. 

This is perfectly harmless under most circumstances. But after heavy snow and ice, these movements could seriously damage your windshield wipers. 

Rather than leave them on, pull them off from the windshield, so they stretch outwards rather than lie on the windshield. This will prevent them from freezing on the windshield and breaking when you start the car. 


We hope this article helped you sort through the facts and myths about car heaters and batteries. While it’s always better to only use the energy you need to power your car, it won’t hurt your car! 

Idling your car can cause unnecessary pollution and doesn’t significantly improve car performance. Be mindful of the planet, and allow your car enough time to melt the ice before making your journey! 

Ultimately, it’s up to your personal preference about whether or not to leave your heater on or off. Fortunately, new cars will not suffer due to your choices, and you can drive easily. 


USA Today: Frigid? Mechanics say skip warming up your car’s engine

RX Mechanic: Frequently Asked Questions (FAQs)

Canada Drives: This Is How Long You Should Warm up Your Car in Winter…

CDC: What is Carbon Monoxide?

Telegram: Car Talk: Should accessories be turned off when shutting off the car?