7 Reasons Your Car Heater Isn’t Working Properly

You jump in your car on a cold, wintery morning and crank the heat up. But after a few minutes, if your car heater is suddenly blowing out cold air instead of heat in the middle of a bitterly cold winter, you have a good reason to be frustrated.

Unreliable car heaters can make the cold winter months practically unbearable. Learn what’s keeping you away from enjoying your car’s warm air and what you can do about it.

Reasons Why Your Car Heater Blowing Cold Air

Several things can potentially go wrong with automotive heaters because, much like a home heating system, there are many components working together to heat your car. If one or more of these issues is present, your vehicle may blow out cool air rather than heat.

A heater can stop working for a number of reasons, including:

  • A low antifreeze/water level in the radiator due to a leak in the cooling system.
  • A bad thermostat that isn’t allowing the engine to properly warm up.
  • A blower fan that isn’t working properly.
  • Coolant that contains rust particles or becomes otherwise contaminated and is blocking the heating core from circulating air into the cabin properly.

Depending on the problem, different types of repairs could be required. There really isn’t a heater unit, like a furnace in your house, that you can just replace.

It is more a combination of different things that provide heat into the vehicle. It’s very difficult to give a cost due to the wide variety of possible problems.

car heater not working

Let’s take a look at each of these issues more in-depth…

Reason #1: Not Enough Coolant

Your car uses coolant – usually made up of 50% antifreeze and 50% water – to cool your engine down, especially during the hot months of summer. During the winter when you crank up your heat, the coolant is brought over from the engine to the heater core that then blows warm air into your car.

It can feel cool for the first few minutes because the engine has to warm up in order for the coolant to heat up and provide heat to your interior.

If cool air continues to blow out, the first thing you should check is your coolant level. When your car is low on coolant, it won’t be able to send any to the heater core to create warm air.

Reason #2: Faulty Thermostat

If you notice that your thermostat gauge stays on the “C” even after the engine has time to heat up, you may have a broken thermostat. If the thermostat can’t signal to the car that the engine is warm, the coolant won’t be sent over to provide heat to your heater core and the air will stay cool.

Thermostats are a relatively easy and inexpensive fix, so installing a new one can get your heater working again quickly.

Reason #3: Problems with Heater Core

Car heater problems are also frequently associated with heater core difficulties: coolant may not be traveling through the heater core properly, the air from the blower motor is not reaching it or there’s a clog in the small tubing of the heater core.

Heater cores, in a nutshell, are cooling system parts that resemble compact radiators. A heater core is made up of brass or aluminum tubing that carries the hot coolant in and out, along with fans that disperse the heat released by the coolant.

A heater core is responsible for a vehicle’s defrosting and heating actions. Heater cores are typically situated directly in the back of dashboards.

If your car is not blowing warm air into the cabin and the coolant level is fine, then you could have an issue with your heater core. If you suspect that something is amiss with your car’s heater core, watch for these signs:

  • Fog inside of your car
  • A fruity, sweet-smelling odor
  • Your car using coolant very quickly
  • The engine overheating

Reason #4: Broken or Clogged Heater Controls

Sometimes after using the control buttons for several years, they can get gummed up and stop working. If the coolant levels are fine and there doesn’t seem to be a problem with your heater core, you may need to replace some of the control buttons or your heater control valve.

The heater control valve is underneath your hood and acts as the switch that turns the heat on and off. If that piece is not working right, your car could get stuck blowing cool air into the cabin.

Reason #5: Faulty Blower Motor Resistor

If the blower motor resistor is broken, you might have issues setting the fan speed or getting air at all.

Reason #6: Water Leaks

The last common problem with car heaters is a water leak. There are many different places leaks can surface, so be sure to check your hoses, radiator, and water pump for damage. If any of these three are leaking, your car heater won’t work properly.

An effective heating system can make for a much more enjoyable winter. If you notice any of these issues or can’t get heat to blow out of your vents, contact a reputable local auto repair shop to look at your heating system.

It’s important to address problems with car heaters as soon as possible. If you ignore the problem, it may cause a bigger and more costly issue down the road.

Reason #7: Faulty Wiring or Blown Fuses

Similar to your broken HVAC controls, your car’s wiring could be broken or have a short in it. This would mean the heater isn’t triggered when the driver commands it to function. Not good.

Here’s How to Fix a Broken Thermostat

To assuage your fix-it fears and show you just how easy DIY repairs can be, The Drive put together an easy-to-follow guide on how to fix a broken thermostat. You will need to purchase a new coolant and a new thermostat.


Working on your car can be dangerous and messy, so here’s exactly what you’ll need to ensure you don’t die, get maimed, or lose a finger and that you keep your jeans, shirt, and skin spotless, hopefully.

  • Mechanic’s gloves
  • Safety glasses

Everything You’ll Need to Fix a Broken Thermostat

We’re not psychic, nor are we snooping through your toolbox or garage, so here’s exactly what you’ll need to get the job done.

Tool List:

Parts List:

  • Coolant
  • New thermostat

Organizing your tools and gear so everything is easily reachable will save precious minutes waiting for your handy-dandy child or four-legged helper to bring you the sandpaper or blowtorch. (You won’t need a blowtorch for this job. Please don’t have your kid hand you a blowtorch—Ed.)

You’ll also need a flat workspace, such as a garage floor, driveway, or street parking. Check your local laws to make sure you’re not violating any codes when using the street because we aren’t getting your ride out of the clink.

How To Fix a Broken Thermostat

  1. Let the car cool for 15 to 20 minutes.
  2. Locate the thermostat. It will be at the base of the radiator, in between the core and the main hose.
  3. Remove the radiator cap.
  4. For better clearance, lift up the front end of the vehicle.
  5. Place a bucket underneath the radiator and drain the coolant by detaching the hose.
  6. Remove and replace the thermostat.
  7. Reattach the hose to the radiator.
  8. Add the coolant and place the cap back on the reservoir.
  9. Lower your car.
  10. Start the engine.
  11. Wait to see if the heat comes on.
  12. Take a test drive.
  13. Check to make sure the coolant level hasn’t dropped.
  14. If it has, refill it as necessary.

You’re done!

How To Fix Low Antifreeze (Coolant)?

The second-most common culprit is that your car has low antifreeze or coolant. Thankfully, it’s far less time-consuming than replacing your thermostat. All you’ll need is a funnel and a new coolant. Ready?

  • After letting the car cool, remove the radiator cap and place the funnel in the opening.
  • Pour in the new coolant until the reservoir is full. You may need to grab the main coolant hose and physically pump the coolant to ensure there are no air pockets.
  • Replace the radiator cap.
  • Start the car, and check if the heat comes on.

That’s it!

How Much Does It Cost to Repair a Car Heater?

Most heating-related repairs range from $300 to $1,000, but it’s difficult to pinpoint an exact number because of the variety of problems that exist. A decrease in the coolant level or a leak in the coolant system is one of the more common problems.

Similarly, you may ask, how much does it cost to fix a car heater blower?

Know what price you should pay to get your vehicle fixed. The average cost for a blower motor replacement is between $363 and $394. Labor costs are estimated between $87 and $111 while parts are priced between $276 and $283.

How Much Is a New Heater Core? Heater cores generally run between $100-$300. The real cost is due to labor, as heater cores aren’t something most DIYers normally tear into due to their deep locations within the engine bay or underneath the dashboard.

How much is a motor for a heater? On average nationwide, a furnace blower motor replacement costs $400-$600, including parts and labor. A single-speed blower motor costs around $450 to replace while a variable-speed motor costs $600+.

How Much Does a New Thermostat Cost? The average cost of a thermostat is about $45, but if you’re replacing the thermostat, you’ll also need to factor in a new coolant, which will set you back around $8-$15 a gallon.