The Easiest Way to Fix a Car Heater At Home
If you’ve got your car heater not working, don’t worry. It will take from 20 minutes to two hours and the car heater will be working totally fine. And yes, you can do it at home without having to use any special tools.
So, if you’ve got a car heater blowing cold air, read this post and go fix it and treat yourself with something good using the money you save.
Before you start troubleshooting a car heater blowing cold air, it is important to know how the thing works. However, you can skip to the repair part of this article, by all means.
DISCLAIMER: These are just some tips that can help you do minor repairs on your car. The actual results will depend on your understanding and execution of the steps. If you are not experienced in this type of work or think that you might not be able to do it the right way, get the help of a professional.
How Does a Car Heater Work?
The heater on your car uses the heat of the engine to heat the cabin unless you have an EV. Here’s how this works:
- When your car’s engine is running it gets very hot.
- Water is used to take the heat from the engine to the radiator to cool the engine down.
- When you turn on the heater, the hot water is circulated through a heat exchanger in the passenger compartment.
- The blower in the cabin passes air through the heat exchanger, also known as the heater core, and the air gets hot.
- The engine has a thermostat valve that makes the heating system work.
The thermostat valve is a very important component of the heating system for the cabin and the cooling system for the engine. It is responsible for:
- Keeping the engine at the optimum operating temperature.
- Making sure that the hot water goes to the cabin first, before going to the radiator and cooling down.
Now, that you know how the heating system on a normal road car works, let’s see what can cause this system to fail. Only then can we understand how to fix the heat in your car.
Most Common Causes of Car Heater Malfunction
In 90% of the cases, the heater malfunction is caused by one of the three reasons:
- The heater switching system might be faulty.
- The cabin air filter might be choked, restricting the airflow through the heater core.
- The thermostat valve might not be working right.
- The heater core might be clogged.
Let’s now move on to resolving the issue of a car heater not blowing hot air. We’ll start with the most common cause and then move on to the next ones. By the end of this article, you will know how to repair a car heater that’s not working no matter what the reason is.
Car Heater Repair – All Causes
1. Heater Switching System Malfunction
Before we move towards fixing the heater, we need to make sure that the heater is actually being turned on. For this, make sure that:
- No fuse in the fuse box is blown.
- The indicator light for heating (generally on the heater button) is coming on.
- You listen to a small clicking sound from the dashboard when you turn the heater on.
- If your car has an automatic climate control system, make sure you have dialed the temperature all the way up.
- Make sure that the AC is off. If both are turned on at the same time, they simply cancel each other out.
If the heater system is turning on and you still don’t get hot air, try the next.
2. Fixing Car Heater Not Blowing Hot Air Due to a Choked Cabin Air Filter
Just like your A/C at home, the air conditioning and heating systems in the car have an air filter. The purpose of this filter is to provide you with clean air while making sure that the heater or A/C heat exchanger does not get clogged.
If this filter gets choked due to lack of maintenance, this can lead to both the car heater and ac not working.
However, this is the easiest to fix and won’t take you more than 10 minutes.
To do it:
- Locate the cabin air filter in your car. It is usually behind the glove box. You can consult the owner’s manual or the internet for the exact location.
- Take the filter out and check its condition. If it has a lot of dust and leaves in it, you need to replace it.
- Get a replacement filter from a local parts store and replace it.
Prop tip: Make a habit of changing the cabin air filter with every oil change. Your A/C and heater will function better and their life will be extended.
3. Car Heater Repair – Faulty Thermostat Valve
If the cabin air filter on your car is in good shape and you are still stuck with a car heater not working and blowing cold air, the next thing you need to check is the thermostat valve. Here’s how you can do that:
- Park the car on a leveled surface and engage the e-brake.
- Make sure the car is not hot. If you’ve come from a drive or if the engine has been running, give it some time to cool down.
- With the car engine cold, open the hood and locate the radiator.
- On the top of the radiator, there’s a large hose going to the engine.
- Trace the hose and locate the thermostat valve (a metallic part on the rubber pipe usually where it enters the engine).
- Double-check that the car is cold.
- Take the thermostat valve out and check it.
- If the spring in the valve is loose and can be pressed easily, the valve is bad.
- Replace the valve with one having THE SAME TEMPERATURE RATING.
- Top the coolant up with distilled water if you have spilled some.
- You are good to go.
This mostly solves the problem of any car heater not working. If your auto heater is blowing cold air even after this, or if the thermostat is in a good condition, you might be in for a little bit of trouble – a faulty heater core.
Fixing a Car Heater – A Faulty Heater Core
The heater core is the heat exchanger that heats up the air in the cabin. The salts and rust in the coolant can block the fine tubes in it. If that happens, not enough hot water can circulate through the core, resulting in insufficient or no heating.
This problem is best left to the professionals because it requires the disassembly of the whole interior of the car. Here’s how you can do it.
- Go to the engine compartment and remove the terminals of the battery. This will prevent the airbags from accidentally going off as you’ll be taking the dashboard off.
- Open the dashboard of the car and take it out. It’s easier said than done. You can find the detailed procedure on YouTube.
- Locate the heater core (a miniature radiator) and take it out.
- Check the heater core by passing water through it or by simply blowing into it. If the core is blocked, get a new one and replace it.
Note: If you have an old car or a rare one, you might not be able to get the core from a parts store. A local scrap dealer might be able to help you there.
That pretty much sums up all cases of car ac heater repair. Let’s address some of the frequently asked questions on this topic.
Frequently Asked Questions
It might be because the engine is still cold. Let it warm up then try again. If the heating is still not sufficient, you can move on to the diagnosis and repair procedures we’ve outlined above.
This can be due to a choked cabin air filter, a failed thermostat valve, or a faulty heater core.
Start by changing the cabin air filter, if that doesn’t work, replace the thermostat valve, if even that doesn’t do it change the heater core.
There might be a problem with the switching system that turns on the heat when you press the respective button in the car.
This problem is usually in cars that have an idling stop feature. If the engine is turned off for a long time when you are stuck in the traffic, this can lead to poor circulation of hot engine coolant in the heater core leading to poor heating. To fix this, force start the engine and rev it up to make the hot coolant reach the cabin heater’s core.