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Car heating gets cold when idling

Why Does The Car Heating Get Cold When Idling?

Winters can get really harsh if you are living in a country closer to the poles. Especially if you are living in a landlocked area. Fortunately, you have heated homes, shops, and offices in many places. You also have the heating inside your car to keep you comfortable in your commute from point A to B. But have you ever experienced the car heating get cold when idling or you are waiting in traffic? This post will help you figure out why.

The heating function of your air conditioner is closely tied to the engine temperature. When you are idling, the engine temperature is lower. Hence the car heating can get cold over time when you are idling or stuck in a traffic jam. Another possible reason for your car heating getting cold while idling is low coolant levels. In this case, it can be fixed very easily by just adding some more coolant to the reservoir.

It is important to note this phenomenon is prevalent only in gasoline/diesel engine vehicles. It does not happen in electric vehicles, mostly because there is nothing such as idling. You can read about this in detail below.

Why does the car heating get cold when idling?

Cold Temperature on thermometer
Image Credits: Pixabay

Engines have a coolant circulating through them to ensure that there is no overheating. This coolant gets hot during circulation and its temperature is closely related to the temperature of the engine. The hot coolant is then used to heat up the air that blows in the passenger cabin. This is how the heating system of a car works.

The amount of heat produced by the engine depends on the speed at which the engine is running and the amount of force it is exerting. When your engine is idling, it is basically running at the lowest speed possible and is barely exerting any force – the bare minimum again. That’s why the engine is not as hot. As a result, the coolant that cools the engine isn’t very hot either. Hence, the heating of your car can get cold when idling.

To help with this problem, newer cars have a slightly different system in place. They have heating coils that are powered by the battery/generator of the car. There is also a sensor that detects if the engine coolant isn’t hot enough for the passenger compartment. At such times, it redirects some electrical power to these heating coils. This along with the radiator of the coolant helps you stay warm enough even under the harshest of conditions.

How can it be fixed?

Well, as mentioned above, the reduction of heating is bound to happen. Especially if you are driving in an old car that does not have the heating coils built in. However, the heating should not reduce instantly – it should take some time. If the heating reduces relatively fast, then it means that the amount of coolant in your system might be low. Due to low coolant, the amount of hot liquid in the whole system is less and thus quickly cools thanks to the fan. You just need to check the coolant level and top off the reservoir according to the recommended mark.

If the coolant level is good, then you can’t do too much. The best you can try is to put the car in neutral gear and rev it up a little bit in hopes of increasing the engine temperature. Or you could just choose to buy an electric car next time!

What happens in Electric Vehicles?

Electric car Tesla
Tesla EV | Image Credits: Unsplash

Well, firstly there is no idling in the case of EVs. When you wait in a traffic jam, the motors simply stop. This is because you can get almost full torque and standstill conditions unlike in internal combustion engines (ICEs).

Secondly, like the heating coils mentioned above, EVs simply use more of them to provide heating. Since they are powered by very large batteries, energy is abundant. However, because the battery is being used to power the heating system and not the motors, this means that the effective range of the vehicle reduces. And this is a huge discussion regarding the development of EVs as customers already deal with range anxiety.  But more on this topic later.

Final Thoughts

Hopefully, this article helped you realize why the heating of your car can get cold when you are idling. As you saw, this is bound to happen, especially if you are using one of the older cars. Sometimes, it can be fixed easily by just adding some coolant. In other cases, you could take it to a mechanic or try the trick mentioned earlier. In either case, we hope that the inside of your car always stays warm.


Abheek is an Engineering student with a background in Automotive Engineering and Sustainable Energy Engineering. He has worked in Engine Development for a couple of years but is quite interested in Electric Vehicles too! In his free time, he likes to use his knowledge to help others with their car problems. Other times, he can be found following the sport of Formula 1.

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