Why Your Car Won’t Heat Up


It can be extremely uncomfortable to drive in a car that has no heat and will not get warm. Some have bundled up as they live in the Arctic but that is no way to live or drive. 

Several reasons exist on why car won’t heat up. They include low antifreeze or coolant levels, a faulty heater fan, a bad thermostat, a faulty blower motor resistor, a clogged heater core, a leaky radiator, bad HVAC controls, faulty wiring, blown fuses.

Some of these things can be easier to fix than others. It’s best to go with the easiest and cheapest fixes first before plunging into a complete reworking of your heating unit. 

Read on to find about about each of these problems and how to fix them.

Low Antifreeze or Coolant Levels

The easiest and cheapest thing to check is the antifreeze or coolant levels. All you have to do to check the level is open your car hood and look at the antifreeze or coolant reservoir to see if it’s low.

They are clear on many newer model cars. 

You should wait until it’s cool if you plan to remove the radiator cap to check or add coolant.

Another thing to consider is the type of antifreeze or coolant you’re using. Colder temperatures make a car react differently and you may need a different type of chemical in the winter than in the summer. 

You may also have the wrong chemical. Some cars require certain types of antifreeze and coolants and putting the wrong kind in can mess up your car’s heating and cooling system. 

Your coolant may also be contaminated. That means there could be junks, particles, and other contaminants in it that are causing a malfunctioning of the heating core. 

Keep an eye on the levels once you fill up your antifreeze or coolant. It doesn’t evaporate so you could have a leak if you experience low levels quickly. 

Read: Can You Mix Green and Red Antifreeze?

The Fan May Stop Working

Figuring out if the fan is working or not is simple. You usually can hear and feel it in the car. The big symptom of a faulty fan is if no air blows out when you turn on the heat. The heating core may be fine but the fan isn’t blowing it out into the car. 

The problem could be a blown fuse. The fuse can be checked by looking at the corresponding fuse to the fan, typically found in a fuse box under the dash near the steering wheel. Replace the fuse and see if that works. 

You may need to replace the fan if that doesn’t resolve the problem. 

Read: Why AC Compressor Runs, But Won’t Take Refrigerant?

Thermostat Failure

A thermostat failure is another common problem when the heat doesn’t work. The thermostat is supposed to open so the coolant can flow. That allows the core to produce heat. 

A failed thermostat doesn’t open, resulting in the core producing no heat. 

Handy people can fix a broken thermostat with a drain bucket, wrenches, a jack, coolant, and a new thermostat. You will need to let the car cool, lift the front of the car with the jack, and remove the radiator cap. 

You will need to drain the radiator by detaching the hose. Then it should be easy to remove and replace the thermostat. 

Reattach the hose, add more coolant, and place the cap. Lower the car and start it to see if the heat works. 

Read: What Happens If The Car Engine Coolant Is Low?

Bad Blower Motor Resistor

Now we’re getting into the less common problems with functioning heat. A broken resistor means you won’t be able to set the fan speed or have it blow air. You will need a mechanic to fix this. 

Heater Core Clogged

Somethings trash and debris can get into your heating and cooling system and clog up your heater core. Sometimes, it’s rust from the radiator, and sometimes it’s just junk that gets into the radiator. 

You will either need to refurbish or replace your heater core. 

Radiator Leaks

This is a common problem when you find you are losing coolant. Coolant isn’t getting to your heater core and eventually, this can damage your engine. 

There are some stop leak products for temporary fixes but you will need to check hoses and the radiator to find the leak. Either the hoses or the radiator may need replacing. 

Read: Temperature Gauge High But Car Is Not Overheating

Bad HVAC Controls

Your controls for your heater may have an electrical short, be broken or the touchscreens are malfunctioning. You will need a mechanic to fix this type of problem. 

Bad Wiring, Blown Fuses

Your vehicle may have some issues with its electrical system. There could be a short in the wiring or something may be broken. It will take a diagnostic to figure out exactly where this problem lies.

Preventive Maintenance

A few basic checks on a routine basis can prevent your heater from failing. Check your fluids regularly and make sure they remain clean. Make sure you are using the correct coolant for your vehicle. 

Pay attention to your fan to see if it is sputtering or having issues. Check your fuses at least once a year and replace those that are bad. 

You can also test the thermostat if you think that is the problem but that isn’t part of any type of regular maintenance. Remove it from the car and place it in water to see if it opens at the right temperature. 

Read: Why Car Won’t Defrost Windows


Is there a way to heat my car without a heater?

Absolutely not. Any method you can think of to heat a vehicle without a heater stands a greater chance of setting your car and maybe yourself on fire. That includes electric, propane, and battery-operated heaters. 

Do I have a heater fuse?

Yes, there are all types of fuses for most functions of your car. Your heater has a fuse and it’s in the fuse box, usually located under the dash. You will need to check your owner’s manual to find out which fuse it is. 

A blown fuse can easily be replaced even if you don’t have mechanical skills. 

Why is my car blowing cold air when I turn on the heat?

It is likely your heater core is bad and it will need to be replaced. 

How much does a new heater core cost?

A new heater core typically costs between $100 and $300. However, that is just the part and you will still need to pay for labor. They are hard to get to for fixing so you could pay $150 or more in labor. 

Do I need to flush my coolant?

Yes, the standard rule is to flush your coolant every 100,000 miles or every five years. However, you may need to do it once as winter approaches and then again in the spring depending on your vehicle and the type of coolant you use. 

How does a car heater work?

Fluid from the radiator becomes hot as it runs through the engine. It runs through the piping leading to the car’s cabin. That’s where the heater core has the hot coolant. The fan blows over the core and sends the warm air into the car’s cabin. 

The cooled coolant goes back into the engine. 

My heater works but why isn’t the air getting warm?

It could be a blockage in the line or a clogged heater core preventing the coolant from getting to the heater core. It could also be a faulty valve or switch.

Check the coolant level after the engine cools and then check the line and the heater core for clogs.

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