Does Car Heater Work When Engine Is Off? (Explained)

Car heaters are essential when external temperatures are low, and for you to comfortably drive your car to your destination.

In freezing temperatures heaters can also be used to melt the ice around the windscreen and give you warmth.

But when you are required to take a break and park your car does your car heater still work and blow hot air? Let’s find out

Let’s Find Out If Car Heater Still Blows Hot Air When Engine Is Off?

Most car heaters do not produce heat when the engine is off. Those that do rely on battery power, and only run for a short time until the existing hot air from the vent chambers is used up as the engine stops generating heat when switched off. The make and model of your car determine how your heater operates when the engine is off.

The best way to find out if your car’s heater runs after the engine is off is to turn on your car and heater, and let them run for a few minutes.

Once the car is warm, shut it off, not the heater module or climate control, and see if the heater continues to run.

You can also experiment with the process by opening your car door to see if the heater shuts off or by timing the period between when you shut off your car and when the heater turns off and stops running on the battery backup.

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Will I Get Hot Air If The Engine Is Switched Off And Cold, But The Heater Is On?

In most cases, the heater will not blow hot air if the engine is off and had been cold.

The heater draws heat and gets its power from the engine, so it’s not possible for it to blow hot air if the engine is not running.

It also takes a few minutes for the air that is blown from the heater to warm up when the car starts since the engine needs to be warm first and reach its optimum operating temperature.

Depending on the engine and how long it has been off, it could take between three and five minutes for the heater to warm up.

During this time, the air coming from the vents may feel cold or cool, even though the heater is turned on.

Some vehicles do have heaters that run off battery power for a short time and will continue to circulate air and heat when the engine is not running.

This is known as backup power.

The amount of time the heater continues to run depends on the make and model of your vehicle.

Will I Get Hot Air If The Engine Is Switched Off But Engine Has Been Warm, And Heater Is On?

Unless your heater operates with a battery backup, your car heater module will not blow air if the engine is off.

Newer vehicles do continue to blow hot air for a short time until the hot air is depleted from the vent chambers after the engine has been shut off, and others stop blowing hot air as soon as the engine and heater control module is off

If your car continues to blow hot air. It may stop once you open the door or after 10 to 20 minutes, depending on your vehicle.

Most heaters require the engine to be on and hot in order to blow hot air. Even if the engine is hot and the heater is on, the engine cannot supply the heater with warm air if it is turned off.

Will Blasting The Blower At The Maximum Make Any Difference?

Blasting the blower while your engine is off will not allow the car to push heat through the car.

If you are hoping to keep the car warm when the engine is turned off, it can be a good idea to get as much heat in the car as possible when the engine is running.

Blasting the blower at maximum can add a lot of heat to the car and keep it warm, but once the engine is off and the backup battery period is over, the heat will stop blowing and the car will gradually cool off until you start the car again.

What Cuts Off The Car Heater?

The car heater control switch is responsible for cutting off the heater. However, when you shut off the engine, the power to the heating element is also cut. The heater relies on this power to operate.

If your car is running and your car’s heater is not working, one of the common problems below could be to blame:

Bad Heater Core

Like small radiators, heater cores serve as heat sources. The fans disperse warm coolant material outside and inside your car through aluminum tubing.

The air blower becomes stuck inside the small tubes when the heater core can’t let coolant through. The heater in your car won’t function at all as a result.

The heater core is likely to be the culprit if the rest of your car’s heating system works just fine.

Look for these signs in your car’s heater core if you suspect something is wrong.

• The interior of a car becomes foggy
• There is a rapid consumption of coolant.
• The smell of your engine overheating
• A car that smells sweet or fruity

Low Coolant

Also, low coolant levels in the heater core can prevent the heater from working.

When the coolant level keeps dropping in your car, there is no heat inside. The cabin or car stays cool, so you don’t have to worry.

As a result of the engine working too hard and not being supplied with enough coolant, it runs out of coolant.  The coolant can be refilled if this is the case.

Thermostat Problems

A rusted old thermostat will not allow the engine to get warm enough, so it will not function properly. Your car needs a thermostat to maintain a safe temperature.  A car’s cooling and heating system works properly when the engine does not overheat.

Bad thermostats will prevent the engine cooling systems from keeping the car’s interior cool, resulting in excessive heat buildup.

Your thermostat should be checked and repaired before it causes further damage to your automobile.

Heater Control Problems

It is possible to turn on and off the heater of your car by using the controls on the heater. There may be wiring problems. It can cause the car’s heater to malfunction. Make sure your switches are functioning properly by checking them and replacing them if necessary.

Air Pockets

In the heater core, air pockets could also be the cause of a heater that doesn’t work well. Generally, an airlock occurs when the coolant system has been drained and filled recently.

A pocket of air in the heater core prevents coolant from flowing through the engine coolant passages. Inspect the heater core and heater hoses to see if the coolant is flowing. 

In normal conditions, the engine should be running at normal temperature and the heater should be on.

Final Thoughts

In most vehicles, the heater will shut off when you turn off the engine. This is because the heater relies on power from the engine to function.

Some vehicles do provide limited battery backup power that keeps the heater on for a short time after the engine has been shut off.

Sources

Does Car Heater Work With Engine Off – Quick Answer (recaro-nao.com)

Car Heater Stopped Working – Symptoms, Causes & Fixes – Rx Mechanic

Car Heater Not Working : Reasons Why and How To Fix It | The Drive