Informational Guide

Heater Blowing Cold Air?

Ever wondered why is my heater blowing cold air? Learn why car and home heat systems can cause these issue and how to fix them.

by Josh M

A heater blowing cold air can be the most frustrating experience during the winter season. Plus, you’ll be missing out on the benefits of a heater. In addition to improving your well-being, having a heater in the home or car offers advantages for structural and electrical components.

When the heater starts misbehaving to the point of blowing cold air, you need to fix it immediately. And, from cars down to central heat pumps, fixing a heater that’s blowing cold air requires you to identify the cause.

The good news is you’re on the right track. Here, I’ll explore the probable causes of a heater blowing cold hair. I’ll also go one step further by describing DIY fixes I have used to repair faulty HVAC systems.

Here’s the info you need.

While there are many reasons the heat is on but blowing cold hair, the culprit is a function of the individual system. The type of heater in question determines the potential causes of the operational problem. 

Central Heat Pumps

A central heat pump is expensive and difficult to install. As such, a central heat pump blowing cold air can be a real source of worry. Since it’s a complicated system, the answer to why is my heater blowing cold air in this context is a multi-pronged one.

Heat Pump Gas Energy

The faulty component can be any of the following:

The Fan Is Off

The central heat pump’s fan is more or less the most important part of the heater itself. The fan controls the blower, which is in turn responsible for circulating air around your home.

If you set the fan to “Off,” it’ll be impossible for the blower to circulate hot hair. Similarly, you should be wary of leaving your fan settings on “On.” Doing so means the fan is always working regardless of whether the device is heating air.  Therefore, the heater will keep blowing cold air instead of warm air.

More often than not, the answer to why my heater is blowing cold air lies with the fan settings. It’s best to change it to “Auto.” This way, the fan will only work when the device is heating air. At this point, the only air available for the fan to circulate through your home will be hot.

Extinguished Pilot Light

In a central heat pump, the pilot light is there to keep your heater warm all through the heating period. The pilot light is a small flame that helps the heater pick fire to fuel the heating process.

Newer heater models tend to have electric pilot lights which stay on indefinitely. Conversely, furnaces older than a decade will have pilot lights that may go out.

If your pilot light is off, you may want to check out the gas supply to your central heat pump. If the gas supply is faulty, there’s no way the furnace will get lit; talk less of circulating hot air.

You can always fix a supply problem by replacing the gas source. However, if the pilot light doesn’t turn on afterward, the central heat pump may require deeper troubleshooting.

Dirty Flame Sensor

The flame sensor contributed to air movement through the ducts. It also determines how much warmth the burner produces.

To check for this fault, try restarting the heater system. If the air feels hot before it gets cold, a dirty flame sensor is behind your heater is blowing hot air.

A dirty flame sensor means you’ll have a burner that won’t stay lit. While it may seem natural to clean a dirty flame sensor yourself, it’s best to leave it to the professionals. It’s a complex job that requires opening the burner and uncovering the flame sensor.

Clogged Filter

Before hot air comes out, it goes through an air filter to ensure its purity. The filter removes debris and other contaminants. Over time, it’ll absorb dirt and become dirty.

If your heater is blowing cold air, check for a dirty filter. If it is, check the size and buy a suitable replacement filter. That should solve the problem.

Thermostat Changes

Most of the time, when your heater is blowing cold air, the culprit is usually the thermostat. Someone in the home may have mistakenly changed the thermostat settings, causing the heater to blow hot air. Or it may be that you need to replace your thermostat’s battery.

Heater Turned On

Car Heaters

As long as the car heater is in great condition, winter doesn’t exactly stop anyone from driving. If your car heater isn’t doing its job, here’s why:

Not Enough Coolant

Coolant liquid cools your car engine during the hot summer months. But it’s also crucial to the car heating process. The presence of coolant in the heater core is important for effective car heater operation.

Sometimes how to fix a car heater blowing cold air is as simple as checking the vehicle’s coolant level. If the coolant level is low, the heater system won’t send any to the heater core to produce warm air.

Heater Core Problems

The heater core is the part of your car heating system that takes the coolant across. It looks like a radiator made with either brass or aluminum.

Sometimes coolant liquid may have an obstructed travel path through the heater air. Or it may be that air isn’t reaching the heater core system. An overheating engine indicates a bigger problem with the heater core.

Broken Or Clogged Heater Controls

Heater controls may develop faults with constant usage. If it’s a minor issue, you can easily change the buttons. Although, in most cases, you’ll have to call a professional to fix the heater controls.

Dysfunctional Thermostat

Sometimes troubleshooting a car heater that is blowing cold air requires taking a look at the thermostat.

The thermostat signals the car heater the engine is warm, thereby kick-starting the car heating process. If it’s faulty, it’s best to buy a replacement thermostat.

Water Leaks

Water is essential to a car heater’s operation. If there’s any water leak, it’ll affect how the car heater works—including blowing cold air instead of hot. Check components like the hoses and radiators to confirm if there’s a leak.

Person in Long Black Sleeves Driving

Chevy Truck Heater Blows Cold Air

The car heater in a Chevy truck is similar to the average car. Fixing a Chevy truck heater that blows cold air will follow the same process as in the previous section. Check for similar faults with your truck.

Because the average Chevy truck is heavy-duty and tends to take a lot of beating, it’s susceptible to water leaks. Check for water leaks before you start to inspect the thermostat and other parts.

Also see – portable truck and car heaters

RV Heater Blowing Cold Air

Below are the top causes for an RV heater blowing cold air:

  • Low battery voltage
  • Stuck sail switch due to rust, debris, or insects
  • Faulty propane system due to hose or valve damage

People Also Ask (FAQ)

How do you know if your heater is on?

Most heaters have a power-on signal to indicate the heater is on. Another way you can check is through the sound of the heater while it’s working.

How many years does a heat pump last?

The number of years a heat pump works depends on the type of system you choose and how often you use it. But a mid-range heat pump will last for close to five years.

How can I heat my car without a heater?

Heating your car without a car heater may not exactly be possible. However, having a hot beverage, covering the windows, and wearing head warmers can help you feel warm in a car.

How can I make my car heater hotter?

You can try to ensure your car heater is in excellent condition at all times. After that, always ensure the car heater is set to the highest possible heating settings.


For a central heat pump system, a dirty flame sensor may be why your heater is blowing cold air. For a car heater, it may be issues with the coolant or heater core.

Use the tips above to find the problem and fix it. Good luck!

Last Updated on December 17, 2021

Josh M

My name is Josh and I am obsessed with the HVAC industry. I created this website to help HVAC techs of all levels get the best out of their heating & cooling systems. I have spent thousands of hours studying air conditioners, heaters and home air products so you can learn & buy with confidence. Learn more about the team here.