Why Is My Car AC Heater Not Working?

The heater is not the mysterious beast where most make out to be. This heating system consists of a heater fan, cooling system, heater core, and HVAC control. As hot coolent is drawn into the heater core, the heater fan is controlled by the HVAC control. It blows the heat into the cabin as the cooled coolant return back to the system. It is a very simple system.

There is a lot of different ways a car AC heater not working, but the problem manly occur either of the two main reasons. Either the coolant is not flowing through the heater core or air from the blower is not blowing directly through your heater core.

Why Car AC Heater Not Working?

There are several issues you can face with the AC heater. It is a little complicated than that is the practice but below there are the most common issues you will be going through

1. Not Enough Coolant

The car uses coolant which is made up of 50% antifreeze and 50% water.  To cool your engine down especially during the hot month of summer this coolant is used. During the winter when you crank the heat, the coolant is brought over from the engine to the heater core then blows warm air into your car.

At first, it cools for few minutes because the engine has to warm up to coolant to heat up. Then provide heat to the interior. In case cool air continues to blow out, the first thing is necessary to check the coolant level. When your car is low on coolant, it won’t able to send any of the heater core to create warm air.

2. Heater Core Problem

One of the reasons can be the heater core problem that is coolant may not be traveling through the heater core properly. The heater core is the cooling system part which is made up of brass or aluminum tubing that carries the hot coolant in and out. Along with the heater core, fans are attached that dispersed the heat released by the coolant. The heater core is situated at the back of the dashboard.

If your car is not blowing warm air into the cabin and the coolant level is fine, you could have an issue with the heater core. Now in case, you do not know how you can identify the heater core problem, here are a few symptoms. Some symptoms are fog inside the car, fruity sweet-smelling odor, your car using coolent very quickly, and engine overheating.

3. Clogged Heater Control

After using the button for several years they can clog and stop working. The coolant levels are fine and there is no problem with your heater core, you need to change the control button. It can also be the reason for the coolant valve. The heater valve is under the hood and acts as a switch that controls on and off the coolent, Thus, the car ac heater not working due to the clogged heater control.

4. Thermostat Disfunctional

The engine gets warmed up but still, the thermostat remains in the C, you may have a problem with the thermostat. And in case the thermostat can’t signal the car that the engine is warm-up, the coolant doesn’t send the heat to the heater core. Thus, the air will stay cool.

For this case, you have to install a new thermostat to fix the problem of the car ac heater not working.

5. Leakage Of Water

The common and easy problem of car ac heater not working is leakage of water. There are many places where leakage can occur. So check the hoses, radiator, and water pump for damage. In case you notice any leakage, it is the issue of not working.

6. Faulty Heater Fan

You may be getting hot coolant in the heater core. This can occur due to the heater fan breakage that can cause electric shock. The heater fan is the part of the heater that blows the heat into the cabin.

7. Faulty Blower Motor Resistor

In the case of a faulty blower motor resistor, you can notice the problem with the heater. This issue can be noticed in the fan speed.

How To Fix The Issue Of AC Heater Of Your Car?

Working on a car can be dangerous and messy. So always wear the mechanics gloves and safety glasses. To fix the problem here exactly what you will need to do.

  • Before starting the process of fixing the issue, first, collect all the handy tools. Tools such as drain buckets and wrenches.

  • You will also need a flat surface such as garage floor or street parking to do the fixing work.
  • Make sure the car engine is cool. In case it is not then make it cool for 10 to 15 minutes before starting to fix it.
  • Locate the thermostat. The thermostat is the base of the radiator n between the core and main hose.
  • Remove the radiator cap.

  • For better performance, lift the front end of the vehicle.
  • Place the bucket under the radiator and drain the coolant by detaching the hose.
  • Add the coolant and place the cap on the reservoir.
  • Lower your car.
  • Start the engine.

  • Wait to see if the heat comes or not.
  • Take a test drive.
  • Make sure that the coolant level doesn’t drop.

How Much Does The New Thermostat Cost?

The average cost of the thermostat is 45$, But if you want to replace the thermostat, you need a factor for a new coolant. This will cost around 8$ to 10$.


Most heater cores are designed for having long use life. The average life span is 10 to 15 years. In case you put a strain on the heater core or fail to find the fault. As a result, the life span can be shortened.

An effective heating system can make a much more enjoyable life in winter. In case you cannot find the issue or fix the issue on your own. Call the repair shop immediately to look at your heating system. It is important to address the car heater problem as soon as possible.

Leave a Comment