12 Common Furnace Problems (and How to Fix Them)

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“Is it chilly in here, or is just me?” If that’s the question that brought you to this post, we’d like to say this first: That stinks. No one needs a quitter furnace in the dead of winter, and we’re so sorry it’s happened to you. And now for the good news: Many furnace issues can be resolved simply, quickly, and inexpensively. In this post, we cover 12 of the most common problems, how to fix them, and when you’ll need some professional help with your Columbia furnace repair.

We’re know you’re cold, so we’ll dive right in.

Furnace Problem #1: The Thermostat Isn’t Set to Heat

We don’t mean to be the HVAC equivalent of the stereotypical IT “help” desk, but we have to at least ask: Is your thermostat actually on—and on the right setting? Even if you’re certain it is, go check. It’s possible someone accidentally switched it off or made an overly aggressive temperature adjustment. It’s also possible that your thermostat batteries died. We’ll keep our fingers crossed for you while you check.

Furnace Problem #2: Furnace Isn’t Receiving Power

OK, well… since you’re still reading, it appears we didn’t cross our fingers card enough. (So sorry.) If your thermostat is operating and its settings are correct, the next “Boy, do I feel dumb” thing to check is this: Is the furnace plugged in? We know it seems ridiculous to think it somehow got unplugged, but it’s absolutely worth a look before exploring other possibilities. 

If your furnace is plugged in, check to see if the circuit breaker tripped. 

  • If the breaker controlling the furnace is in the OFF position, flip it back to ON. 
  • If it’s between ON and OFF, flip to OFF before switching it to ON. 
  • If it stays in the ON position, assume the tripped breaker was a fluke, and breathe a sigh of relief.
  • If the breaker trips again, you may have a problem with the wiring or with the breaker itself. In either case, you should involve a licensed electrician.

Furnace Problem #3: Furnace is Making a Grinding or Scraping Sound

If your blower is producing a grinding or scraping noise, it means your ball bearings have worn out and you should turn off the unit immediately. For this fix, you’ll need some help from a qualified Columbia HVAC professional. 

Furnace Problem #4: Furnace is Making a Squealing Noise

Shrieking furnaces indicate a slipped or worn blower belt. If you’re reasonably mechanically inclined, you can likely tackle this repair on your own. 

  • If you can’t see any damage to the belt, try tightening it. (Just don’t overdo it, or you’ll end up with Problem #3.) 
  • If you can see wear and tear on the belt, pick up a new one from your home improvement store, and follow the replacement instructions in your owner’s manual. 
  • Oooooor… save yourself some significant time and hassle, and let us help you instead.

Furnace Problem #5: Pilot Light or Ignition Issues

If you have an older furnace with a pilot light that won’t stay lit, you’ll need a professional to help you investigate several possible causes. You could have a misbehaving thermocouple or a clogged pilot orifice, your flame setting may be too low, or you might have a defective safety switch (which is obviously a big deal).

Note: Before attempting to relight your pilot, turn off the gas supply and wait several minutes. Natural gas is highly flammable, and if your pilot light has been out for some time, there could be a dangerous amount of gas built up around the unit. Always follow the instructions in your owner’s manual. 

For furnaces with an electric ignitor, it’s worth checking the condition of your flame sensor. This critical safety feature of your furnace shuts down the whole works when it detects gas but no flames. When these sensors get dirty, they can’t “see” the flames, and so they unnecessarily shut everything down. To clean yours:

  • Turn off power to your furnace at the unit itself or by flipping the circuit breaker (not just at the thermostat).
  • Close the gas supply valve. 
  • Using a ¼” hex-head screwdriver, carefully remove the flame sensor—it’s a thin, metal rod located at the burner assembly.
  • Gently rub the sensor with fine grit sandpaper or an emery board. (A dollar bill actually works great, too!)
  • Wipe away any remaining dust with a paper towel, and then replace the sensor.

Furnace Problem #6: Dirty Filters

We cannot over-exaggerate the importance of regularly replacing your furnace filters. Clogged filters restrict airflow, which makes your furnace work harder, which can lead to the heat exchanger overheating, which will shut down your unit. 

At best, you’ll have an inefficient furnace producing less heat for more money. At worst, you’ll shorten the lifespan of your furnace and have a chilly house. If your furnace isn’t producing enough heat, or if it’s constantly cycling off and on, there’s a good chance the poor thing is gasping for air. Replace those filters!

Furnace Problem #7: Access Panel Left Open

As you’ve no doubt discovered, accessing the guts of your furnace requires opening a panel on the unit. If the panel isn’t closed all the way, the furnace will absolutely not turn on… yet another safety feature to prevent injuries!

Furnace Problem #8: Dirty Burners

If your burners get gunked up, they can’t release sufficient natural gas to create combustion—which means you’ll get no heat. Healthy burners produce blue flames; any other color, such as yellow or orange, indicates debris in the mix. Dirty burners can also produce an impressive boom-rumble when they try to ignite. Although Googling “how to clean dirty burners” will yield several results, we strongly advise against doing this yourself. Too many things can go wrong—and quickly.

Furnace Problem #9: Cracked Heat Exchanger

A cracked heat exchanger hampers your furnace’s ability to do its job and it can allow deadly carbon monoxide to seep into your home. The signs of a cracked heat exchanger can be tricky to spot, but they may include:

  • Soot on the inside of your furnace
  • A strong, unpleasant odor that may remind you of that frog dissection unit in 10th grade biology
  • Water on the floor around the furnace
  • People in your home experiencing headaches, irritated eyes, nausea, disorientation, or flu-like symptoms—all indications of carbon monoxide poisoning

If you even suspect your furnace has a cracked heat exchanger, shut it down and call in a Columbia HVAC expert immediately.

Furnace Problem #10: Faulty Limit Control Switch

If your blower fan runs continuously, and you’re certain your thermostat is set to AUTO not ON, your limit control switch may be to blame. This switch, located just under the box that directs heat from the furnace to the ducts, shuts down the system when the air gets too hot. If the unit never shuts off, it means your limit switch needs to be adjusted or replaced—which is a job for an HVAC pro.

Furnace Problem #11: Furnace Doesn’t Blow Air

If your furnace is coming on but it doesn’t seem to be moving air, you probably have a broken blower fan belt. As we advised in Problem #4, follow the instructions in your owner’s manual to replace the belt (or let us do it for you).

Furnace Problem #12: Popping or Pinging Ducts

As ducts heat, they expand, and when they cool, they shrink back—which can explain most of the popping or pinging sounds you hear. You may also have a loose flap of metal inside a duct that wiggles as air moves past it. If you can trace the sound to its exact location, try making a small dent in that location to see if that stops the sound. (Hooray for physics!)

Could Your Furnace Use a Tune-Up?

To ensure your furnace will keep your home comfortable all season long—and for many years to come— have us over to do a thorough inspection. With MasterTech Plumbing, Heating and Cooling, Columbia’s most trusted HVAC experts, you can have peace of mind that we’ll take good care of you and your home. But you don’t have to take our word for it; check out our reviews!

We had a great experience with Mastertech Plumbing from the time we made the phone call to request service. Our plumber Tyson was friendly, knowledgeable & professional. I would highly recommend this company & him for any plumbing needs.
Jamie Hogan
Jamie Hogan
17:40 22 May 20
I had a clogged drain that needed professional assistance. MasterTech was able to get Devin out to my house to fix our issue in record time. Devin was great and very professional and made sure the issue was fixed, the work area was clean and that I was satisfied with his work before he left. I highly recommend MasterTech.
Jeffery James
Jeffery James
17:01 08 May 20
When I called, the phone was answered by a pleasant service representative that remembered me and was understanding to my immediate need. MasterTech Plumbing tech Chad was very professional and friendly. He kept me informed of all what was wrong and didn’t try to up sell anything. I really appreciate Chad’s skillful knowledge. The quality of his work is exceptional. I know I can rely on Chad and MasterTech Plumbing.
Angela Hernandez
Angela Hernandez
02:12 08 Apr 20
The service we received today was awesome! Punctual, efficient, and up front and honest about prices and what products that we needed. Excellent work.
Cole Stoecklein
Cole Stoecklein
14:52 18 Mar 20
Josh is great! He is the one who usually comes to our house. He installed an overhead tank toilet, which is a tricky and time-consuming job. He overcame many obstacles and stuck with it until the job was completed and done right. Price was also good. MasterTech has always taken care of all our needs in a prompt and professional manner. Emergency service has always been rapid too.
Michael Lewis
Michael Lewis
17:24 11 Mar 20
Chris was great. Dispatch was great. We were scheduled quickly. Prices were very competitive. Edit: We had great success having our pipes fixed. Due to Missouri weather things were touch and go but Master Tech sure delivered! We are so please with the fix, financing and friendliness Master tech and our technician Chris Gilpin provided us. Will forever and always us Master tech. Certainly mighty nice people
Kimberly Threatt
Kimberly Threatt
01:30 29 Feb 20
We had to have emergency service today, Saturday. A serviceman was here in less than an hour. The repairs were made quickly, the charge was not over the top, even though it was not a work day, and the individual was friendly and courteous. We have learned to expect this kind of service from Master Tech. Thank you.
Barbara Timbrook
Barbara Timbrook
03:48 26 Jan 20
I recommend MasterTech. They show up when they tell you they will show up. They provide a comprehensive estimate and also a good explanation of the work that need to be done. Their work is good quality. They usually have the needed parts on their truck so they can do the task in a timely manner. They clean up the work area after the job is finished,
Dennis Catlett
Dennis Catlett
22:15 23 Jan 20
A great experience. First, on time, service tech was sent out when promised. Second, quick assessment of the problem (faulty sump pump). The tech not only quickly replaced the pump, but he made an alteration that will make it easier whenever a replacement has to be made. Bottom line, a most professional service. Certainly would recommend Master Tech to folks needing their service.
W B Tichenor
W B Tichenor
16:08 31 Dec 19
MasterTech is so great to work with. They're quick, clean, do great work, and have fair pricing. But the best thing about MasterTech is their people. Whoever is responsible for their human resources does a terrific job of selecting and/or training them. They're so friendly and provide excellent information and customer service. I highly recommend MasterTech!
Jason Black
Jason Black
20:37 26 Dec 19
Previously I had not been impressed with master tech. However, their technician Dillon not only fixed my emergency pipe break at 1am on a holiday but also saved me as a customer. This was the best service I have ever had at my home. He arrived promptly at 1am. Provided a couple of options on how to fix my problem both in the short and long term and quickly made repairs. He also has provided advice on how to address issues related to the water damage caused by the busted pipe. This was one of the most positive bad situation we have had as homeowners. Thank you Dillon and mastertech.
Michael Grote
Michael Grote
20:35 26 Dec 19
I had to change my appointment at the last minute and they were able to accommodate my new availability without any hesitation. My tech was really professional (Dillion). I got a call and a text to let me know he was on the way. He fixed my problem quickly and was so friendly. This is the second time that I have had to use a plumber and I will use Master Tech again since I have an old house with old plumbing.
Leigh Burton
Leigh Burton
14:01 22 Nov 19
HVAC and plumbing under one roof, what else do you need?! Great team!
CJ Roe
CJ Roe
01:06 30 May 18

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