Troubleshooting a Non-functional Heater with a Working AC (Causes & Fixes)

Heaters always seem to crap out on the coldest days of the year, which can be ridiculously frustrating. If you are waiting for a repair person or looking to fix it on your own, there are several different things to look for and understand about this system! Having a good understanding of your heater can help you fix it independently, but also know when you need some help.

Your heater may not be working due to a cracked pilot light. Broken draft motors, faulty ductwork, and clogged air filters are all very common reasons for a malfunctioning heater. Some of these issues can be fixed by yourself, while others are dangerous and need the help of professionals.

Broken heaters can feel overwhelming and frustrating to understand if you aren’t familiar with them. But you are in the right place. This article will go over the common reasons for broken heaters and how to identify and fix them. So let us continue and learn all the information you need to fix a busted furnace!

Troubleshooting A Heater That is Not Working 

Finding out what particular problem plaguing your heater is the best way to learn about the appliance and how to fix it. Identifying these problems can help determine if you can solve them on your own, or if you need to call a professional. If you have this problem, go through the checklist below to get to the root of the problem!

Power Off To The Heater 

When your heater is not working, the first step is to turn it off. This not only prepares you for the investigation but will save you that wasted energy on your next bill! Turning the heater off will let all the systems cool down so you can look into the ducts and heater safely.

This power-off may also give your heater the break it needs to make repairs easier. Maybe the heater is like your router, and simply needs a quick reboot to start working! Either way, turning off the system is certainly your first step to finding the issue.

Clogged filters and ductwork

It is a real possibility that the problem with your heater is not the actual heater itself, but rather the ductwork. If your HVAC system is pretty old, the ducts may be broken or the filters clogged with debris. These occurrences could block the warm air from reaching you, which could appear as the system is not working.

Poor installation could be another reason for faulty ductwork. So if you had your system recently installed this could be the cause of the issue. Some professionals cut corners when doing ductwork which can lead to improper airflow.

A clogged filter could also lead to improper air flow and even lead to the system overheating. This could lead the heater to break and stop working altogether. So it is always good to keep your air filter clean and duct system checked on to make sure these do not become issues in the future!

Mechanical issues 

There are a good amount of mechanical issues that could be messing with your furnace. Each of these issues has different items to look for and ways to fix the issue. So if you are still having issues with your furnace, take a look at these components.

The first mechanical issue could be a dead blower capacitator. This is a large battery-looking piece that starts your furnace when the thermostat tells it to. If this piece is dead it could keep the blower from starting, which is what pushes the heat around your home.  A dying capacitor leads to a blower malfunction, which can be a costly fix. 

The next issue could be a faulty heat exchanger.  This problem can sometimes be an effect of other issues such as low airflow and dirty components. But it is a very serious problem as this exchanger contains CO2. If it is cracked or damaged, the toxic air could leak into your home and make you sick. So you will always need to replace it if it is cracked for safety. 

Then there is the issue of a bad inducer draft motor. This piece helps clear the heat exchanger of leftover gas from the last heating cycle and then vent all that air outside. If this component begins pulling in high amps or gets dirty it can burn out after a while. HVAC professionals often check to make sure this piece is working properly but needs to be replaced if broken. 

Finally, there is the bad heat pump.  Not all homes utilize a heat pump, but if you do it could be an explanation for your issue. Your refrigerant may be too low which can cause the heat strips to come on more than they should which can get expensive. If you notice these heat steps come on frequently, you will need to increase your refrigerant charge.

Pilot light is out 

The pilot light element of your heater is what keeps the warm flame going from the gas valve at the base of the furnace. If this goes out then the heater will fail completely. So if you have a gas or propane-powered furnace this could cause the heat to go out while the air conditioner still works!

Luckily, this is a pretty easy fix! To start you will need to turn off all the electrical components and breakers related to the furnace. This is an important safety measure when you are working on the furnace. If you open the front access panel of your furnace and the flame is out, then this is your heating problem.

All you need to do is relight the flame. Most of the time you will only need to press the priming button in your furnace. If that does not work then you will need to manually light it with a long lighter, but this is pretty rare. If you smell or hear gas leaking from the furnace, do not light it! This can lead to an explosion, and tell you there is a leak with the valve of your pilot light.

Too Much Gas 

Not all furnaces operate in the same way and they need to be calibrated to work properly. There is usually a specific setting that determines how much gas the furnace burns. If this calibration is off, the furnace could be burning too much gas. And this can lead the heater to malfunction and stop working.

This overuse of gas can lead to your energy bill being higher than it needs to be. But it can also make your furnace overheat. If this is the problem you are having, you will need to call a professional to help recalibrate the system. It is a simple fix, but one that an expert needs to do to avoid messing up the calibration more.

Can I troubleshoot these problems myself? 

You can troubleshoot furnace issues on your own! It is the best way to figure out the exact issue and see if you can solve the issue without needing to call someone in. Here are a set of steps you can take to investigate the issue.

First, you will want to make sure your thermostat is set to heat mode, just to rule out that it may be off accidentally. You can change the batteries in your thermostat to see if there is simply a communication error between the thermostat and the furnace!

Now you will want to ensure that the circuit breaker is ON and the breaker for the furnace has not tripped. Then look for the furnace ON button to be sure that the unit is not switched off. This button is usually inside the furnace cabinet. 

If none of these efforts have worked, keep trying! Now it’s time to see if the motor in your furnace is overloaded. There is usually a simple restart button close to this motor. If you press it and nothing happens, wait 30 minutes and then try again.

Finally, try turning off the power to the furnace at the main electrical panel or sub-panel. You will then take at the fuse on the power switch. If you have seen that it is blown, then you just need to replace that fuse!

You can also go through the checklist in the earlier section to see if one of those common pieces may be damaged or broken. But if you have looked through every possibility and still found no explanation, then it is time to call someone. 

When should you call a professional?

Calling in a professional is never the most exhilarating thing to do, but there is a point where it becomes necessary. If you have gone through all the checklists so far in this article, you have likely found the cause of the heaters issues. If the problem is a thermostat that needs more batteries or a dirty air filter, then that is an easy fix to do on your own!

However, if you have noticed the pilot light is cracked or the draft motor is broken, these are the times to call in professionals. It is much safer to allow them to install picky machinery and do it properly. That way you will not have to worry about the same problem just a few months down the road!


Furnaces can be picky for a number of reasons. Some of their parts might be aged, which keeps them from working properly. While other pieces have been poorly installed and created a chain reaction of different broken parts. This article is a great start to figuring out the specific issues with your heater, and hopefully helps you deal with problems with more confidence!

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