Car Heater Blowing Cold Air – 10 Possible Reasons

Many car owners encounter the problem with their heater blowing cold air.

The bad news is that you can run into this during cold mornings when driving to work. It will not only be frustrating but may also ruin your day!

Therefore, although it is an uncommon problem, its cause should be diagnosed and fixed as soon as possible. But what brings this issue?

The heating system can run into several problems described below, resulting in the car heater blowing cold air.

10 Reasons Why Your Car Might Be Blowing Cold Air

Faulty Thermostat

The thermostat regulates the flow of the coolant in the engine. It does so by opening or closing its valves when the engine’s temperature reaches a specific level.

For instance, if the thermostat detects that the engine is warm, it will open its valves, thus allowing the coolant to circulate in the engine.

However, if the thermostat malfunctions, it will stay open; hence the heater will blow cold air. Luckily, fixing this problem is pretty straightforward.

You will only have to install a new thermostat. However, using the car’s manual is advisable since poor installation might cause additional problems.

Malfunctioned Heater Core

The heater core is a component in your car that allows the coolant to flow to and from the engine. If it malfunctions, it will make the heater blow cold air.

This system can malfunction in different ways. For instance, the coolant may have impurities that clog it.

Therefore, you should check if it has gone faulty whenever your car feels cold. One way of diagnosing it is by using a non-contact thermometer.

If the thermometer doesn’t change its reading, the coolant is not flowing in the heater core.

But if you don’t have the thermometer, you can check its condition by observing if there’s fog in the cabin or if the engine is overheating.

If you notice the two signs, you have a faulty heater core. Fortunately, this problem doesn’t need you to take the car to a garage.

All you need is a cleaning fluid to flush out the impurities. But don’t be too happy!

There are instances where you might be required to install a new heater core. For example, if the heater core is broken beyond repair, you will have to replace it.

The Blend Door Is Jammed

The blend door is a component that rarely undergoes regular maintenance. It is usually maintained alongside other parts such as the water pump.

If these other components don’t run into problems, it makes it hard to check the condition of the blend door.

Therefore, it may be responsible for the heater blowing cold air.

This component enables the air to circulate between the heating system and the internal components in your car.

The air will not pass through the heater core; hence, it will only blow cold air. So, you will have to check if the air passes through the heater core.

If it does not, you have a jammed blend door that needs to be fixed.

The Coolant Level Is Low

Your car’s engine has a coolant fluid, water mixture, and antifreeze fluid.

This coolant prevents the engine from overheating and supports the heating system. If the coolant runs low, you will receive cold air in your car.

So, you should check the coolant level whenever the car heater blows cold air into the car. But it is advisable to let the car engine cool first before doing so.

Topping it up will solve the problem if you deduce the low coolant level.

But this might be a short-lived solution since the low coolant level indicates another issue. Therefore, you should also check what made it do so.

It could be an issue with the gasket or the hose. Hence, you might also want to check these two components to ensure they are fine.

If one of them is faulty, you must repair or replace it to prevent the coolant from running low again.

Presence Of Air In The Heating System

It may sound like a minor issue, but trust me, it can also be responsible for the heater core blowing cold air.

Since the heater core is located at a high point in the cooling system, it is susceptible to air entry into its components.

The presence of air in the heater core will interrupt its coolant temperature. For instance, it will make the warm air-water mixture cold.

It will, in turn, be blown into the cabin as cold air. The good thing is that you can quickly sort out the problem by flushing out the air bubbles.

You can check how to do so on Youtube. However, flushing out the air bubbles is a temporary solution; hence, you should also find out what is letting in cold air and fix it.

Damaged Heater Control

Your car has a heater control located underneath the hood and is made to turn the heat on and off.

Like any other feature in your car, the heater control can also malfunction due to old age or reckless usage.

For example, its button might get damaged, giving you the impression that the heater is on yet off. In such a circumstance, the heater might get stuck blowing cold air.

Therefore, you should also examine the heater control for damages to avoid being blamed for the heating issue.

In most cases, if the coolant level is optimum and the heater core is in good condition, the problem is in the control buttons or valves.

But if the valves are fine, you have damaged heater control buttons that need to be replaced.

Damaged Water Pump

The water pump supplies water to the air-water mixture in the heater. If this feature gets damaged, it will let out water.

As a result, the coolant fluid will not have the right amount of water, and as you already know, a less optimal air-water mixture might make the heater blow cold air.

So, it would help if you also examined the water pump when looking for what’s causing a heating issue.

The best thing is that a leaking water pump will have water bubbles on its outside surface.

If you can see these bubbles, you might want to replace the water pump to eradicate the cold air in the cabin.

The Blower Fuse Is Blown

As you know, the heater needs voltage to heat the air-water mixture. Therefore, if there is no voltage reaching the heater due to a blown fuse, the heater will blow cold air.

This blower fuse can blow up for several reasons, such as electric short or old age. Fortunately, you can quickly check if the blower fuse works well using a voltmeter.

If it has gone wrong, the only way to fix the heater issue is by replacing it.

But it is vital that you also check what has made it blow up since replacing a blown fuse is a short-term solution.

If it is due to an electric short, rewiring the circuit will solve the problem completely.

An Issue With The Cables

The cables can also make the car heater blow cold air. It happens when they are worn and unable to supply voltage to the heater.

The cable terminals may also be loose hence not making proper contact. So, you should also check their state when you encounter a heater issue.

If the cables are corroded, you have to replace them with new ones. Also, tightening their terminals might solve the problem if they are loose.

However, it is essential to take extra caution when handling them since they can cause shocks.

The Safety Feature Is On

The safety feature will be activated if the heating system overheats to prevent fire or carbon monoxide leaks. When this occurs, the heater will only blow cold air.

But it would help if you weren’t concerned since this is a good thing. This issue will go away on its own once the heater has cooled off.

But it is good to check and fix what made the heater overheat in the first place.

To Sum Up

A car heater that blows cold air should be a significant concern to you.

It is because it not only makes the car’s cabin cold but also indicates an underlying issue with the heating system’s components.

These components include the thermostat, blend door, heater core, water pump, blower fuse, and cables.

It may also indicate that the coolant fluid has run low or that the heating safety feature is on. Therefore, you should diagnose these parts and fix them appropriately.

You should also check the coolant fluid level and top it up to sort out the problem.