Updated at: 15-07-2022 - By: Lucas

When traveling in the winter, it is normal for the air blown by the engine to get cold. In this section, I will explain why the car’s heater gets so cold at idle.

If your car’s heater isn’t heating up at idle, you may want to check out some of the most typical causes of heater failure or heating issues.

In some ways, the reasons the heater vents cold air while idling are similar to those discussed in the blog post.

5 reasons why the car’s heater blowing cold air when the engine is idling

Car Blows Cold Air When Stopped-2

The heater is frigid at idle for five major reasons.

Low coolant level in the expansion tank

At idle, your heater may be blowing chilly air because of a low coolant level in your tank.

Using the same type of coolant to finish the coolant level is a simple and fast remedy.. Check the radiator or expansion tank cap if coolant is dripping continuously but there are no evidence of leaks.

This is a warning sign that you should not ignore, as it could lead to more serious problems and damage to your engine. You should check your car’s manual to see if the coolant has been out for a long time and/or is in poor condition, and if so, you should replace it with a new one of the same type.

A bad or failing water pump

It is the rotor’s job to move coolant through the cooling system, and if it is unable to do so, the heater will blow cold air while the car is idle and warmer air when it is moving. If the pump is to blame, a new one must be installed.

A dirty or clogged heater radiator

Car Blows Cold Air When Stopped

When the heater’s radiator becomes clogged, it becomes difficult for the coolant to circulate through its bearings, resulting in slightly warm or fully frigid air being vented at idle. The radiator can be cleaned to see if any cracks have formed where liquid or air can escape.

Most of the time, even at idle speed, cleaning the heater’s radiator improves efficiency.

A bad or worn thermostat

It’s possible to have cold air pushed out of the engine while the thermostat rod is stuck open. It will take a long time to warm up a cold engine if the coolant is cycled in the huge circle first.

Problems with the climate control system.

This system, especially on newer models, might have software difficulties, resulting in chilly air being vented by the car’s heater when it is at idle. An incorrect system configuration or software or hardware issues with the climate control may be to blame for issues.

The sort of system and the precise model of car you have will dictate how you go about checking its operation. In most cases, the owner’s manual will walk you through these stages. The information can be checked by oneself if it exists. If you can’t fix it yourself, it’s best to get in touch with a mechanic.

Air in the cooling system

Incorrect coolant replenishment, depressurization of particular pipes or connections, malfunction of the air valve, difficulties with the pump, or a broken cylinder head gasket can all contribute to the presence of air in the cooling system.

The heater only blasts hot air when driving and cold air while idling because air in the cooling system obstructs coolant circulation.

The coolant supply is blocked

Rust has closed or jammed the heater’s coolant supply tap, if it has one, to the radiator. The simplest way to fix this problem is to open the tap on an older car’s heater. Rust will build up in the tap if you use too much water and not enough coolant.


Checking the coolant level and condition is the quickest and easiest approach to fix the problem of the heater venting chilly air while the car is idling. Next, examine the water pump, thermostat, heater’s radiator, heater’s tap, and the presence of air in the cooling system.

This signals an issue with the cooling system of the engine, which can lead to more serious and expensive difficulties in the future, therefore it’s best to have the situation checked out as soon as possible to avoid these complications.