What Causes Car Heater to Blow Cold Air?

Check to see if the temperature control is set to cold. If you’ve been driving with it on hot and something has happened to switch it over, this could be the culprit.

Look at your temperature gauge. If it’s not very high, that’s probably why your car is blowing cold air.

Check your engine oil level If your engine oil is low, that could mean that there aren’t enough lubricants in the engine and therefore not enough heat generated by the motor to heat up the cabin.

Blocked Heater Hose

One of the most common causes is that your heater hose is blocked.

When this happens, it can prevent hot air from being pushed through your vents and into the cabin of your car.

This can also cause water to build up in front of the vent, which will further block airflow.

You can check this by removing some panels in your engine bay and looking for any obstructions in the hose system.

Dirty Air Filter

If you’ve been driving around with a dirty or clogged air filter, it could be blocking airflow into your vehicle’s heating system by restricting airflow through the filter itself, which means that warm air isn’t getting into the cabin as quickly as it should be which results in cold air coming out of your vents.

You should change out your filter every 12 months or 12,000 miles to ensure optimal performance and prevent damage to other components within your car’s heating system as well as reduce fuel consumption over time by increasing efficiency (which means less money spent on gas).


The thermostat is a device that controls how much heat enters your car’s engine.

If the thermostat malfunctions, it will cause your car’s heater to blow cold air instead of hot air. If this is the case, you’ll need to replace it with a new one.

Check the temperature setting

If you’ve changed the temperature setting in your car, that could be why it’s blowing cold air.

Make sure that you’re not accidentally on the defrost setting or something like that.

It’s also possible that if you’ve recently driven through a puddle of water, you may have gotten water into your climate control system, which will make the air feel cold until it dries out again.

Check your fan speed

If your car is blowing cold air when it shouldn’t, try turning down the fan speed to see if it changes anything. If this doesn’t work, move on to step three!

Check for leaks in your HVAC system

If there are any holes in your HVAC system or exhaust pipe, they can cause the car’s engine to overheat and blow hot air instead of cool air into your cabin while driving around town at high speeds all day long!

Air conditioning

If you’re sure the AC is off and still blowing cold air, check to see if the car has a temperature sensor. You may have accidentally turned it on when you were playing with the controls.

Defective blower motor resistor

This is also something that’s best left to the professionals it’s located near where your fuse box would be, and it could be difficult for amateurs to reach without damaging other important parts along the way.


You should also check your radiator hose and the radiator cap for leaks.

If there’s any kind of leak here, coolant will escape from the system and prevent warm air from getting into the cabin efficiently.

Leaks like this can be pretty difficult to spot without professional help.

Hence, we recommend taking your vehicle into a shop for a full inspection if you suspect there may be an issue with either one of these components.

A faulty gas cap.

If this cap isn’t sealing correctly, it could cause fuel vapor to leak out and get into the engine compartment, where it would be ignited by hot exhaust gases under pressure.

This could cause an explosion that damages the heating system.


Your engine is overheating and needs to cool down before you can turn on the heater again.

You might want to take a look under the hood and see if there’s any steam or smoke coming from it that could be a sign that your engine is overheating.

If so, stop driving immediately until things are fixed and call for help.

Your hoses and vents

If there’s a leak somewhere in your system, it will lose pressure and eventually stop working altogether and even if it does work again, later on, it won’t work as well until all of those leaks have been fixed up.


In conclusion, your car’s heating system is complex, made up of many different parts that all have to work together for it to function correctly.

If something isn’t working right, make sure to get it fixed as soon as possible so you can stay warm and comfortable during those cold winter months

Steven Hatman
Steven Hatman

We break down every information into easy-to-understand articles that cover all the categories anyone who owns a car needs to know about, such as oil , brakes , tires and etc. Our car guide is free and updated regularly for you to use as a resource, not only when you have an issue with your car but even before buying a new or used car! We also give tips on what to look for in each category or part of your vehicle.