Furnace Not Working? 7 Common Causes & What To Do

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Is your furnace not working? There are a number of reasons why you may find yourself without heat in the winter – some issues may be simple and quickly resolved, while others are more serious. 

Learn about the common reasons why a furnace stops working as it should: 

1. Issues With Your Thermostat 
2. Your Air Filter Needs Changing
3. Your Furnace Was Accidentally Turned Off
4. There’s Something Wrong With The Gas Line
5. Your Pilot Light is Off
6. There’s a Mechanical Problem 
7. Heat Exchanger Damage
8. What To Do If Your Furnace Stops Working

If you are concerned that your furnace is not working properly, contact Service 1st. Our experienced and professional team of HVAC Technicians have been helping homeowners in the Cambridge area for over 30 years. 

Note: No matter how big or small you think a problem is, ALWAYS contact an experienced HVAC company to look at your furnace if it stops working. Do not try to fix or even touch anything yourself – you could make the problem worse, hurt yourself, or void your warranty.

7 Common Reasons Why Your Furnace Is Not Working As It Should

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1. Issues With Your Thermostat

Sometimes, if your furnace has suddenly stopped working, the issue is not actually with the furnace itself. It can be difficult to differentiate this on your own since your thermostat controls your furnace. If your furnace isn’t turning on at all but is relatively new, there is a good chance that your thermostat needs batteries, needs to be replaced, or needs to be fixed. 

Fortunately, checking the thermostat is a very simple job for your HVAC Technicians to complete, and they can quickly tell you if the thermostat is the cause of your issues or if it is the furnace itself. A professional HVAC company will also be able to give you expert recommendations on what to do if it is your thermostat – it might be time to replace it or you might want to use this as an opportunity to upgrade your thermostat to one that has more features, such as a a smart thermostat

2. Your Air Filter Needs Changing

It is generally recommended that you change your air filter every 3 months (90 days) to ensure your HVAC system works optimally. If you didn’t know this and haven’t replaced your filter regularly, it can cause your furnace to stop functioning as it should. 

Your furnace’s air filter does an excellent job collecting dust, hair, and other tiny particles. If it has been too long since it’s been changed, it can collect a very large amount of particles and begin restricting the air flow to your furnace. If this happens, your furnace will likely still work and turn on, but you may notice a significant decrease in how well it is functioning. 

If you notice that your furnace isn’t running properly but still turns on, contact a local HVAC company to come take a look. If the problem ends up being a simple air filter change, they can let you know right away and provide you information on how to best maintain your furnace so that this problem doesn’t occur again.

3. Your Furnace Was Turned Off

Furnace not working? Yes, it is possible to accidentally turn off your furnace!

Many homeowners don’t know this, but your furnace can actually be turned off. For most furnaces, this can often happen one of two ways. The first is that your furnace somehow got ‘unplugged’ (yes, it can happen!) 

Most furnaces have a switch that looks like a regular light switch. If you accidentally turn it off or bump into it without noticing, you could turn off your furnace.

Another way your furnace can get turned off is if the circuit breaker has been tripped. Your breaker could be in the “off” position and that would cause your furnace to not turn on at all. 

Fortunately, if either of these issues are the cause, there is absolutely nothing wrong with your furnace. While you may feel silly for calling an HVAC Technician just to find out your accidentally turned off your furnace, it is always best to call a professional HVAC company when your furnace isn’t working. 

professional company will never make your feel bad for calling if the problem turns out to be something you think is silly or small! It is much better than trying to fix something yourself and making a small problem worse.

4. There's a Problem With The Gas Line

Any gas-powered appliance in your home can develop issues due to a problem not with the unit itself, but with the gas line. Sometimes, gas lines can get damaged or blocked due ‘normal’ outdoor things like tree roots, insects, and even just dirt. A problem with your gas line is serious. If your gas line is damaged or blocked, it can create a build-up of gas or it can begin leaking gas. 

This is one of the many reasons why it is so important to see a professional HVAC company when your furnace stops working. There are not always obvious signs that there is something wrong with your gas line. If you notice your furnace not working, a professional HVAC company can look for all of the potential reasons – even ones that you wouldn’t be able to see yourself. 

If it turns out that there is a problem with your gas line, an experienced HVAC company will be able to tell you exactly what needs to be done to safely rectify the issue.

5. Your Pilot Light Is Off

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A professional HVAC Technician can inspect all parts of your furnace to help you determine the problem

Not all furnaces have a pilot light. However, many older units do have one. You may have seen a pilot light in your gas fireplace – well, a pilot light in your furnace is similar. If your pilot light won’t stay lit, there are a number of potential causes. If your pilot light is off, you may not know how long it has been off for – and this can lead to potential serious danger. 

When your pilot light turns off, it can cause a dangerous amount of natural gas to build up. While you may think that simply turning your pilot light back on is a simple solution, it is not. As with all of the other potential problems we’ve listed above, never attempt to turn on your pilot light or touch anything in your furnace yourself. 

Furnaces are wonderful machines that help keep our families safe and comfortable, but they also present serious hazards if you try to touch or fix something yourself. If your furnace stops working and you aren’t sure why, or if you notice that the pilot light is off, contact a local HVAC company right away.

6. There Is a Mechanical Problem

Did you notice your furnace making a weird clunking noise, a grinding noise, a squealing noise, or any other strange sound you know just isn’t right, it may indicate a mechanical problem. This simply means that a part or piece within your furnace is broken or isn’t functioning properly.

 If you notice your furnace making any weird noise, you should always turn it off immediately and call a professional HVAC company. Allowing your furnace to continue running may be dangerous and/or it could cause the problem to worsen or create more extensive damage. 

Even if you do not notice any strange or unusual sounds before you noticed your furnace not working, that doesn’t rule out a mechanical issue as the cause of your problem. Only an HVAC company will be able to tell you exactly what is wrong with your furnace after performing a thorough inspection.

7. Your Heat Exchanger Is Damaged

A cracked heat exchanged can cause a CO leak. Learn more about carbon monoxide poisoning in the video above

cracked heat exchanger is one of the most serious furnace problems and poses significant health risks to you and your family. A cracked heat exchanged may not be obvious, and one of the only signs you notice is that your home’s carbon monoxide detector goes off – and it is not a false alarm.

The heat exchanger in your furnace helps to create hot air, which is of course, a good thing! The air inside of the heat exchanger gets extremely hot and it creates a number of gasses during this process. If everything is running as it should with your furnace, this is all perfectly safe. However, if your heat exchanger is cracked, it can pose a serious hazard. 

If the heat exchanger is damaged, it can cause carbon monoxide (CO) to leak into your home. In Ontario, all homes are required to have carbon monoxide (CO) detectors installed. Carbon monoxide is extremely dangerous, and it is known as the “silent killer” because it is tasteless, colourless, and odourless. There is no way of knowing it is in your home unless you have a detector.

A damaged heat exchanger can cause a build-up of uncombusted gasses, which can eventually lead to an explosion or fire in your home. If your carbon monoxide detectors go off, immediately evacuate your home. Learn what to do from the official Ontario website here.

Furnace Not Working? Here's What To Do

You may have seen a common piece of advice given throughout this article – if your furnace stops working, always contact a local, professional HVAC company. Even if you think you know what the problem is, and even if you think it is a minor issue, you should always contact the professionals. Do not attempt to fix any problem on your own. 

Do not touch your furnace at all. If you meddle with your furnace or any of its parts, you could void your warranty, cause an even bigger problem, or get hurt. Furnaces contain harmful gasses and parts that can cause serious injury if you do not know what you’re doing. 

professional HVAC company will have certified and trained HVAC technicians who understand these dangers and know exactly how a furnace works, as well as signs to look out for that something is a serious problem (or a minor one!)

If you notice your furnace not working, don’t panic. It can feel stressful when any large appliance or machine in your home stops working as the unknowns and potential repair costs can feel overwhelming. 

However, when you work with a reliable and trustworthy HVAC company like Service 1st, you will get an accurate diagnosis of the issue with next steps on what to do. At Service 1st, we also are committed to providing you with the final costs up front. You will never experience hidden fees or sticker shock from us. 

We want to ensure that you feel comfortable from the very first call to any necessary follow-ups for repairs or replacements if necessary. If you live in the Cambridge area and furnace is not working and you need to find out why, give us a call. We’re happy to help – even if it turns out that your furnace was simply turned off!

Service 1st: Your Trusted HVAC Technicians Serving The Cambridge Area

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Furnace not working? Need repairs, replacement, or emergency services? At Service 1st, we’ve been serving homeowners in the Cambridge area for over 30 years. Service 1st is a locally owned and operated business. 

We pride ourselves on professionalism and delivering the highest quality work as well as installing the highest quality products. We are an Elite Bryant Factory Authorized Dealer. We have received the prestigious Circle of Champions award from Bryant – an honour that highlights our commitment to quality, leadership, and excellence in the HVAC industry.

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“Our furnace was replaced last year and we were doing our annual furnace service. In doing so, Chris, heard something that didn’t sound right even though it still worked fine. But because of this, he felt that there was a defect in the motor and had it replaced under warranty that could have otherwise cost us a lot of money. Thanks Chris and Service 1st Heating and Cooling for your professionalism and straight up honesty. Would definitely recommend.”

If you are a dealing with your furnace not working in Cambridge or the surrounding areas, we can help. Give us a call today and you will talk with one of our staff right away. When you call Service 1st, you’ll always talk directly with someone who can help – you won’t have to worry about automated voice messages or complicated menus. 

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