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5 Common Furnace Problems & Solutions

February 24, 2023
Dark gray furnace with a Jon Wayne branded sticker centered on the front of it.

Picture this: it's a cold day outside, and you're looking forward to relaxing in your heated home. You turn on the furnace, only for it to start malfunctioning. Unfortunately, this is more common than you may think. Many issues could hinder your furnace's performance, from motor troubles to strange odors. This article covers 5 of the most common problems that plague furnaces, including:

  • Blowing cold air
  • Won’t turn on
  • Short-cycling
  • A strange odor
  • Fan keeps running

Let's get into it!

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Blowing Cold Air

On a chilly winter morning, nothing's more frustrating than turning on your furnace only to be hit with cold air. That said, this is a common issue, so there are a few steps you can take to resolve it.

Solution: Check Your Air Filter, Pilot Light, and/or Gas Supply

  • Air filters - We recommend checking your furnace’s air filter first. If it’s clogged with everyday household dust, hair, and debris, your furnace will experience a blockage in airflow, which can lead to cold air coming out of your vents.
  • Pilot light - If your air filters are in good condition, you might check the furnace’s pilot light (provided it runs on gas). If the pilot has gone out, your furnace won’t produce heated air.
  • Gas supply - If your furnace runs on propane, check the tank to ensure it hasn’t run out.

Do none of these resolve the problem? You could have an issue with the pilot light’s flame sensor (for gas furnaces), the heating elements (for electric furnaces), or another unknown mechanical issue behind the scenes that should be inspected by a trained HVAC professional.

At Jon Wayne, we offer speedy and thorough furnace repairs and tune-ups. No matter the brand or condition of your furnace, our friendly and knowledgeable technicians will quickly identify and resolve the issue.

Won’t Turn On

Is your furnace refusing to turn on? Chances are, something is blocking your system. Once you get rid of the blockage, the appliance should start working again, and you can return to enjoying a warm and comfortable home.

Solution: Check the Air Filters

An air vent located next to a can light on an all white ceiling.

The first thing you should do is check the air filters to ensure there are no clogs. Even a little dust can interfere with airflow and prevent your furnace from properly turning on. If replacing your filters doesn't work, there may be a more complex problem, such as the following:

  • Broken thermostat
  • Damaged gas line
  • Faulty pilot light

In these cases, you'll need an HVAC expert to perform a thorough evaluation.


When you set your thermostat to a certain temperature, your furnace turns on and starts heating. Once it reaches the set temperature, it automatically shuts off and "rests." After a short period of time, it turns back on, and the heating cycle repeats. If your furnace is short-cycling, however, this cycle gets disrupted and turns on and off at the wrong times. When left unaddressed, short-cycling can lead to the following problems:

  • Uneven temperatures
  • Higher energy costs
  • Long-term damage

So, how do you stop short cycling? In most cases, the problem can be avoided altogether through regular maintenance.

Solution: Get Regular Maintenance

A short-cycling furnace is often the result of overheating. If the furnace gets too warm, it automatically shuts down, consequently disrupting the normal heating cycle. Overheating is typically due to one of the following problems:

  • Dirty air filter
  • Clogged air vent
  • Clogged exhaust vent

Schedule regular maintenance to prevent your air filters and vents from getting blocked. At Jon Wayne, we offer a 5-star maintenance plan that covers yearly heating tune-ups. In addition to high-quality service, members enjoy cost-saving benefits and priority scheduling.

It's important to note that overheating isn't the only potential cause of short-cycling -- a faulty thermostat or an oversized furnace can also trigger it. No matter the issue, you can trust the Jon Wayne team to identify it.

A Strange Odor

At the beginning of winter, it's normal for furnaces to emit a burning smell. Over summer, when you’re not using your furnace, dust will naturally settle onto it. Once you turn on your furnace for the first time, any burning odor is just the smell of dust burning off.

However, if this odor doesn't go away after several days, you may have a problem that needs further investigation. Additionally, suppose you smell other odors like rotten eggs or a mechanical smell. In that case, you should have it looked at by a professional HVAC technician, as it could have a more serious underlying issue.

At the very least, you should clean your air filter to ensure optimal and clean airflow throughout your air ducts.

Solution: Furnace Tune-Up, Duct Cleaning, or Furnace Repair

  • Furnace Tune-Up: To prevent burning smells at the start of the heating season, we recommend having your furnace tuned up by a qualified HVAC technician who will fully clean, inspect, and lubricate key components. Not only does this help prevent dust buildup, but you’ll also avoid surprise breakdowns by catching smaller issues before they snowball into costly fixes.
  • Duct Cleaning: Over time, your air ducts will get caked with dust, hair, debris, and even mold. As air passes through your ducts, it will pick up any odors present. If it’s been a number of years since your ductwork was installed and you’re smelling any strange odors, we recommend having them cleaned by trained HVAC professionals. At Jon Wayne, we have more than 20 years of experience helping Texas homeowners keep their ductwork in top-notch condition. Schedule a free estimate for duct cleaning today.
  • Furnace Repair: If you have a sulfur-like odor (think: rotten eggs), contact a licensed and highly-trained HVAC professional immediately. You could have an issue with your furnace’s heat exchanger, which emits this rotten-eggs smell when it’s cracked or broken. The reason for urgency is that a broken heat exchanger will also emit Carbon Monoxide, a lethal bi-product of heat combustion.

At Jon Wayne, we have over two decades of experience in furnace repairs. Whether you notice a faint, burning odor or a strong rotten egg smell, we'll take care of it quickly and to the highest quality. Call (210) 293-6700 or schedule online today.

Furnace Fan Keeps Running

One of the integral parts of a furnace is the fan, which is responsible for pushing hot air throughout the home. Generally, the fan should shut off soon after the heating cycle ends. If it continues running, however, there's something wrong with your system. And, if you want to avoid unnecessary energy costs, you'll have to resolve it quickly.

Solution: Check Your Thermostat

A woman with pink painted nails, holding a mobile phone device while changing home temp from her smart thermostat application.

While a constantly running furnace fan may be frustrating, there's a silver lining: in most cases, it can be resolved by simply checking your thermostat. If your fan is set to "on," it will run continuously. Switching the setting to "auto" should make it stop.

On the other hand, if your thermostat is already in "auto" mode, you probably have a more serious issue (such as faulty equipment). This will require the help of professionals, such as the Jon Wayne team.

Contact the Jon Wayne Team Today

If you're dealing with common furnace problems, contact Jon Wayne. Our NATE-certified technicians will evaluate the issue, devise a solution and provide a free, in-home estimate. And you can trust us to get the job done right the first time.

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