Furnace Not Working: What to Do


There’s nothing more annoying than waking up freezing in the middle of the night, but you can’t simply pull up the covers and go back to sleep? That’d have been nice, but now your HVAC system is having none of that. Why did my furnace stop working in the middle of the night? Why tonight of all nights? You probably feel like kicking the furnace.

Kicking the furnace will most probably not get it to start working. Okay, you may be lucky, and the machine may cough back to life when you kick it. But, the chances of that are very slim – almost zero, and even if it works, there’s still an underlying problem you need to fix. The furnace may get you through the night, but it’ll break down again soon.

That said, it’s not every issue with your furnace that requires the expertise of a professional technician. A little DIY experience may be sufficient to resolve the immediate problem and get your furnace working again. But you can’t fix a problem you don’t recognize. If you can’t tell what’s wrong with the system, fixing it will be a challenging task for you.

Common Furnace Problems and What To Do When They Happen

Your furnace will not suddenly stop working because it doesn’t feel like functioning anymore. Only humans can make such lazy decisions. If your HVAC system suddenly kicks out one night or morning, then there’s a problem somewhere. You’ll need to resolve that issue to get your home heating system to start doing its job efficiently again.

That said, not every problem will cause your furnace to stop working completely. Some will drastically decrease its efficiency, while others may inconvenience you in other ways. However, regardless of the nature of the problem or its effect on the efficiency of your heating system, you shouldn’t ignore it. So, even if your question is not “why is my furnace not working?” We still have answers for you all the same.

So what do you need to do when your furnace stops working or functioning efficiently? You can either call professional furnace repair services or go the DIY route. If you intend to fix the appliance yourself, then consider the following common problems and how to fix them.

Problem — Furnace not Working

What do you do when you discover your furnace is not working? First, identify the fault and determine the best way to fix it. Let’s look at some possible solutions for a sticky situation like this.

Possible Solution – Check if The Device is Turned On

We don’t want to sound like the HVAC equivalent of an IT help desk but, this is not a very rare occurrence. People often forget to turn on the unit, and then they think it’s broken when it won’t start. Okay, you could swear you left the furnace on before you went to sleep; that’s alright. But did you consider someone may have gone there to put it off while you’re asleep? That’s a possibility and shouldn’t be a problem unless you live alone.

Anyway, before panicking or breaking out the DIY queen/king in you, check the power switch or electrical outlet. Make sure to connect and turn on the unit. If that doesn’t resolve anything, you can consider other alternatives but don’t panic.

Possible Solution – The thermostat May be Off Put it On

This point may sound as silly as the first one, but we can’t rule it out of the possibilities. You may think your furnace is not working, whereas; it’s the thermostat that’s off. The thermostat on your furnace should be set to heat above room temperature by at least five degrees.

Nonetheless, you can attempt the following troubleshooting activities on your thermostat once you establish the nature of the problem.

  • Examine the thermostat’s battery. If your home furnace has a thermostat that runs on batteries, then the problem may be with the batteries. You should try switching out the old batteries for new ones and see if it picks up. Ideally, you should change the thermostat’s batteries at least once a year. So, don’t wait until the batteries flash low or go flat before you replace them.
  • Gently unscrew the thermostat and clean out any debris clogging it. Never underestimate the ability of dust to reduce the efficiency of your home appliances. So always get rid of dirt from the components of your appliances.
  • Ensure your programmable electronic furnace reflects the correct date and time. The wrong time may cause problems if the system is set on a timer.
  • Examine the circuit breaker and the fuse of the furnace. There may be damage to the circuit breaker, or something may have disconnected it. A situation like this will hinder the functionality of your furnace.

You can determine if something’s wrong with the circuit breaker by doing a flip test. First, locate the switch controlling the furnace in the home’s breaker panel. If the switch is on, flip it off and on again. That should reset the breaker. If resetting the breaker doesn’t fix the issue, something may be wrong with the wiring in the circuit or the entire circuit breaker.

Possible Solution – Check Safety Switch On the Furnace Door

Manufacturers install safety switches on furnaces to prevent the fan and burner from working while the access panel is open. The safety switch pops out when you remove the furnace door. You’ll need to replace the door before the safety switch deactivates, and the furnace can start working again.

So, if your furnace is not working, the safety switch might be on, or there’s a fault with it. If the safety switch is on, that means the panel door is open, and you need to close it properly. The safety switch should automatically deactivate once you put the furnace door back correctly. However, if the safety switch remains on after putting the door back, something is wrong, and you need to repair or replace it.

  • Use the following steps to troubleshoot the faulty safety switch.
  • Shut the power off and disconnect the furnace from its power source
  • Remove and clean the blower door. Make sure it’s free of dirt and debris.
  • Open the switch panel and rewire the safety switch.
  • Reassemble the safety component, and put the back panel door.
  • Test the installation; if it doesn’t work, you’ll have to replace the safety switch.

Related Article: How Long Does a Furnace Last?

Problem – Furnace Struggling to Produce Heat

A furnace that’s not producing sufficient heat is a different case from one that’s not working at all. But, just like with a furnace that’s not working, a furnace that’s not heating up properly may be due to several problems. So let’s look at some possible causes and solutions to this problem.

Possible Solution – Check and Changed Clogged Filters

Ideally, you shouldn’t have to deal with a problem resulting from clogged filters if you regularly maintain your unit. Cleaning or replacing dirty filters is a crucial part of furnace maintenance and also the easiest.

However, failure to regularly do this simple task can inconvenience you when you’re not expecting it. In this case, the clogged filters may be the reason your HVAC system is not producing enough heat. Or rather, why it’s not distributing sufficient heat. Owing to the aforementioned fact, the dirt in the filters can block the outflow of hot air from the furnace vents. So, the burner may be producing enough heat, but the problem is with the distribution.

You can follow the steps below to take care of the heat distribution issue;

Locate the filter in your HVAC system

Most units have their filters in the intake. The filter should be close to a section that looks like a grate in the floor, wall or ceiling of your furnace.

Check the filter

Checking the filter is a straightforward process. Simply hold it up to the light and see if any light passes through. If nothing passes through, then it’s time to replace it. But then again, holding the filter to the light may not be necessary; a dusty smell from the vents of your furnace is enough proof your filter is done.

Replace the filter

Check The Filter

Turn the furnace off and disconnect it from the power outlet before changing the filter. Then, remove the old filter and put in a new one. Pay attention to the direction of your filter points before putting in a new one. Filters don’t work both ways; they only allow air to move in one direction. As such, installing the filler upside down will prevent hot air from coming out of the furnace.

You should replace your filter regularly not only because a clogged filter might prevent the easy distribution of heat through your space. A clogged filter will also make the air handler work harder to compensate for the restricted airflow. As the air handler is working harder, your HVAC system will overheat, which may cause it to break down faster. Not to mention it’ll drive up utility bills.

Also, you should note that most new furnace designs are more sensitive to clogged filters. So, when the unit begins to experience problems from dirty filters, they’ll shut down to prevent further damage. So, if your new furnace model suddenly shuts down, it may be time to check the filters.

Possible Solution – Check and Clean the Burners

Dirty burners won’t burn well, which will affect your furnace’s heat production. If your HVAC unit is not heating up properly, you may want to inspect the burners for debris.

It’s easy to tell if the burners are dirty or not without putting in much effort. Look at the flames on the burners; are they burning yellow or blue?

Blue light indicates your burners are clean, and everything is good with that part of your furnace. However, if the flame is yellow, your burners are most probably due for a cleaning. Don’t let it surprise you; specks of dust can accumulate anywhere on your appliances, including the burners. Dust buildup usually occurs during summer, so it’s ideal to clean the burners before winter.

The combination of soot and dust can reduce the efficiency of your burner. In other words, it’ll prevent the furnace from producing enough heat, or it’ll make the system work harder to heat the room. That said, the burner may be the culprit when your furnace is not working correctly.

You can use a vacuum cleaner to clean the burners. However, before you start cleaning, ensure to turn off the power and gas supply. Next, wipe the burner clean with a paper towel after you’re done vacuuming it. Lastly, ensure to clean the burners at least once a year and replace them if the need arises.

Possible Solution – Check and Fix a Faulty Pilot Control

Most gas furnaces come with either a pilot light system or an electronic ignition control mechanism. The two components eliminate the need for constant flames to keep the unit working.

Most recent furnaces come with electric ignition systems instead of a standing pilot light. The reason is that ignition systems are better as drafts in a heating system can put out the pilot light. However, ignition systems can also become faulty.

A defective ignition system will reduce the heat production ability of your furnace. This way, it’ll also negatively affect the efficiency of your furnace. You can do the following to troubleshoot the fault with the ignition system of your heating system.

  • First, reset the ignition switch by turning the furnace power off and back on.
  • If resetting the switch doesn’t work, then you should inspect the heating element in the furnace. Turn off the power and gas supply to the furnace. After that, examine the heating element but be careful not to touch it. Look for cracks and other signs of damage on the components. If you find any, it’s time to replace the ignition system.
  • Check the User’s manual supplied by the manufacturer for other troubleshooting activities you can do. Finally, call the technicians if nothing works, even after following all the recommendations from the manufacturer. The problem is beyond you at this point; invite professional furnace repair services to examine the unit.

Other Problems

While the most alarming problem will be that your furnace stops working, several issues can also call for immediate attention. These issues may not threaten the efficiency or functionality of the unit. However, they may inconvenience you in other ways or lead to more grievous problems later on. Below are some of the other issues your furnace can have and how you can troubleshoot them.

Noisy Furnace

Most of the components of your furnace have a metal construction, so they have a higher tendency to make noise. Metals generally conduct noise easily, so manufacturers use different insulations to break the noises.

However, noise coming from your furnace may result in damage to the insulation ductwork of the unit. The obvious solution to this problem is replacing or repairing the flexible insulation ductwork. However, you most probably won’t be able to do that yourself, so it’s better to hire a heating contractor for the job.

Other Funny Sounds from the Furnace

Aside from the general humming sound typical of most home appliances, you may also hear some funny sounds coming from your furnace. You may hear varying sounds like squeaking, popping, rattling, and grinding or grating sounds. Each of those noises has specific issues causing them, and you need to fix those issues to stop the noise.

Your furnace will make squealing noises when the belt connecting the motor to the fan is out of position, or it’s worn out and needs replacement. You simply need to put the belt back into its place or replace it if it’s worn out to stop the squealing noise.

Pinging or popping sounds coming out of the ductwork are usually a result of thermal expansion. I.e. The sounds occur as the ductwork expands and contracts upon heating and cooling. To eliminate this noise, locate the specific point the sound is coming from in the duct runs and make a small dent in the sheet metal around the spot.

Rattling noises usually occur when the fan or the cabinet are not screwed down tightly. Try tightening all the screws on each panel and component of the appliance; it should take care of the noise.

However, you don’t want to make grinding sounds from your furnace lightly. Grinding sounds usually occur when something is wrong with the motor bearings of the unit. Don’t attempt a DIY approach for this problem. Instead, shut down the system and call the technicians for help the minute you discover this problem.

Related Article: 10 Common Furnace Problems and How to Fix Them


Many things can be responsible for the breakdown of your home furnace. But you can’t simply sit on your hands when your furnace is not working. You either attempt to DIY the solution or call the people who can fix it. Or better still, you can purchase a new one. Regardless you don’t want to journey through the cold months without a functioning HVAC system.

Even if you’re a DIY pro, there will always be problems that will be beyond your capabilities. You’ll need professional help with those, and that’s where we come in. Simply call us at ALP Heating if you need same-day furnace repair services. We’ll be glad to be of assistance to you.

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