How to Fix Your Car Heater for Blowing Cold Air When Idle

How to Fix Your Car Heater for Blowing Cold Air When Idle

One of the most common problems people face is that their car heater blows cold air when the engine is idling. It usually occurs in winters because then we use the heater of the car.

Even if you’ve never faced this problem, you should still know why it happens so that you know the reasons if you ever happen to face it.

Why does your car heater blow cold air when idle?

Following are the top 7 reasons that you need to know-

1. A Bad Water Pump

If the condition of your water pump is not good, in that case, it may also lead to your heater blow cold air at idling because this part circulates the coolant through the cooling system. When the rotor cannot create sufficient flow, the heater blows cold air at idling, and when the car starts moving, the air starts getting warm.

2. Air In the Cooling System

If your car’s cooling system has air due to improper replacement of the coolant, malfunction of the air valve, depressurization of the pipes and their connection points, or because of a bad or damaged cylinder head gasket, then it can also cause your heater to blow cold air when idling because the air impedes the circulation of coolant in the system which causes the heater blows cold air at idle and hot air when driving.

3. The Coolant Supply is Clogged

If the heater has a tap for the coolant supply to the radiator, it usually gets clogged or jammed because of rust. This type of heater is found in older cars, and the easiest solution to this problem is to open the tap.

4. Problems With Climate Control System

This problem occurs especially in newer car models because the climate control system can sometimes have software issues which can cause cold air blown by the car’s heater at idle. The issue can be associated with improper configuration of a particular system or with hardware or software problems of climate control.

To check this problem, you’ll require to go through your car’s manual because the climate control system can be different for the different car models. If there’s no such information in your car’s manual, then visit a service center or workshop to get it checked.

5. The Low Coolant Level in the Expansion Tank

A low coolant level in the expansion tank represents a potential reason why you don’t have hot air in the cabin. It’s not just related to when the engine is idle. However, this can be the reason why your car heater blows cold air when idling.

The simplest fix to this problem is completing the coolant level with the same type of coolant. Also, if it seems that the coolant constantly drops without giving any sign of liquid leaks, check the expansion tank cap or radiator cap.

You must not avoid this symptom because things can get serious for your engine. If your car’s coolant hasn’t been changed for a long time, then it’s crucial to replace it with a new one of the same brand or with one that your engine needs.

6. A Bad Thermostat

When the thermostat rod is jammed in the open position, it can cause the cold air to blow when the engine is idling. If the coolant is circulated in the circle in a cold engine, it’ll only be able to warm up after a long time of driving the car, or you’ll require to spend a lot of time warming up when the engine is idling.

7. A Dirty Heater Radiator

The radiator of the heater gets dirty or clogged, which makes it hard for the coolant to pass through its bearings, leading to cold air blowing at idle. You can clean the radiator and check if any crack is created where the air can enter or the liquid can come out.

Now, as you’ve got to know the reasons why your car heater blows cold air at idle, you should know how to fix it.

How To Fix Your Car Heater?

Following are the things that you can do to fix it-

Check the Thermostat

The thermostat is used to control the flow of coolant, which helps the engine warm-up fast and then stay at a steady temperature.

If the engine is cold, the thermostat will restrict the coolant’s flow into the engine, allowing it to warm up quickly. So if the thermostat is not working properly or if it’s jammed in the open position, it’ll not do its job. Make sure you replace the thermostat with a new one.

Check the coolant level

Check the coolant level in your car because, in most cases, the coolant level is low, which causes your heater to blow cold air when idle.

Completing the coolant level with the same type of coolant is the only thing you can do to resolve this problem.

Clean the Radiator

Clean the heater’s radiator well with a cloth and make sure it’s not clogged even slightly.

Check the Cooling system

As I’ve already mentioned that the air in the cooling system can also cause this problem, it’s important to check the entire cooling system. If any part or feature seems improper or in poor condition, get it fixed because that may be causing the air to be in the system.

So this is how you fix your car heater for blowing cold air. If your problem is still not fixed, make sure to get to a professional because there might be some software-related problems preventing your car heater from working properly.


So this was all about how to fix your car heater for blowing cold air at idle. If your car has this problem, make sure you fix it as soon as possible because a poorly functioning heater indicates a problem in the engine cooling system, and if not fixed, it can cause serious issues with your engine, which will cost you very much.

Frequently Asked Questions (FAQs)

Following are some of the frequently asked questions related to car heater-

How much does a new Thermostat cost?

The average cost of a thermostat is around $45, but if you need to replace the thermostat, you’ll also require to factor in a new coolant, which will cost you more.

The cost of a new heater core is $100-$300, but if you need to get it placed in your car, you’ll also need to pay the labor cost because it’s not possible to place it yourself due to its deep location.

The average lifespan of a heater core is about 10-15 years if you take care of it.

You need to flush your coolant every five years or 100000 miles. However, if you’re having any issue with your heater or your car overheating, then you may need to flush it earlier.

Yes, your car heater does have a fuse, and to check if it is shot, you’ll need to locate your fuse box and the fuse for the heater. You may need to go through your car’s manual to find out their location.

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