Top 5 Common Furnace Problems and How St. Louis Homeowners Can Troubleshoot Them

When your furnace isn’t working the way it should, it can quickly turn a cold St. Louis winter day into a stressful situation. From strange noises and weak airflow to systems that won’t turn on at all, furnace issues often show warning signs before a total breakdown occurs.

Some problems can be resolved with simple troubleshooting, while others require professional attention to avoid further damage or safety concerns. Knowing the difference can help you stay warm, prevent costly repairs, and keep your heating system running efficiently when you need it most.

In this blog, the heating experts at Indoor Comfort Team break down the top five most common furnace issues, what may be causing them, and safe steps homeowners can take to troubleshoot before calling in a professional.

1. Furnace Won’t Turn On

There are several reasons why your furnace might not be turning on. Some of the most common causes include:

• Thermostat Settings – Incorrect thermostat settings or dead batteries can prevent the furnace from receiving the signal to turn on.
• Circuit Breaker Trip – A tripped circuit breaker or blown fuse can cut power to the furnace, leaving it unresponsive.
• Dirty Air Filter – A clogged air filter can restrict airflow, which can cause the furnace to shut down as a safety precaution.
• Pilot Light or Ignition Issue – If the pilot light is out or the ignition system is faulty, the furnace won’t be able to start.

How to Troubleshoot:

• Check the Thermostat Settings and Batteries – Ensure that the thermostat is set to “heat” and that the temperature is higher than the current room temperature. If the thermostat requires batteries to operate, try replacing them to rule out potential power issues.
• Reset or Check the Circuit Breaker – Check your home’s electrical panel to ensure that the circuit breaker for the furnace hasn’t tripped. If it has, reset it and check if the furnace turns on. If it trips again, there could be an underlying electrical issue that requires professional attention.
• Inspect and Replace the Air Filter – A dirty air filter can obstruct airflow and cause the furnace to shut off for safety. Inspect the filter and replace it if it’s clogged or dirty. Remember to replace the filter regularly to maintain optimal airflow.
• Relight the Pilot or Check for Ignition Problems – If your furnace has a pilot light, check to see if it’s lit. If not, follow the manufacturer’s instructions to safely relight it. If your furnace uses electronic ignition and isn’t firing up, it could be a problem with the igniter or gas supply, which may require a professional to repair.

One of the best ways to keep your furnace functioning properly from year to year is with routine maintenance. At Indoor Comfort Team, we offer maintenance plans that include no overtime charges, priority scheduling, discounts, and 2 service visits a year.

2. Furnace Blows Cold Air

If your furnace appears to be operating normally but is blowing out cool air rather than its normal warm flow of air, there could be several reasons behind it.

• Thermostat Set to “Fan Only” Mode – The thermostat may be accidently set to the “fan only” mode, causing the fan to blow air without activating the heat elements.
• Dirty Air Filter – A clogged air filter can restrict airflow, preventing your furnace from efficiently heating the air. This can cause cold air to blow out of the vents.
• Gas Supply Issues or Pilot Light Failure – If the furnace is powered by gas, a disrupted gas supply or malfunctioning pilot light may prevent the furnace from heating properly, resulting in cold air.

How to Troubleshoot:

• Check and Adjust the Thermostat – Ensure that the thermostat is set to “heat” mode, not “fan only,” and verify that the temperature setting is higher than the current room temperature.
• Inspect and Replace the Air Filter – Turn off the furnace and remove the air filter. Check for dirt buildup or blockages. If the filter is dirty, replace it with a new one. Regularly change the filter every one to three months to ensure optimal airflow.

3. Strange Noises Coming from Furnace

While most furnaces make some noise during operation, the sound should be consistent and subtle. If you notice new or unusual sounds coming from your heating equipment, there could be an underlying problem. Common noises include:

• Banging or Rattling – Loose parts, screws, and other components in the furnace or ductwork can cause banging or rattling noises.
• Squealing Sounds – These types of sounds are often caused by a worn-out blower belt or motor.
• Scraping Noises – A malfunctioning blower wheel can produce scraping or grinding noises if it’s damaged or obstructed.

How to Troubleshoot:

• Tighten Loose Components and Inspect Ductwork – Check and secure any loose screws or parts inside the furnace. Inspect the ductwork for any loose or disconnected sections that may be causing rattling sounds.
• Lubricate the Blower Motor or Replace the Blower Belt – If the noise is a high-pitched squeal, lubricate the blower motor’s moving parts, or if the blower belt is worn, replace it.
• Inspect the Blower Wheel for Damage or Obstruction – Turn off the furnace and inspect the blower wheel for any debris or damage. Clean it if needed and replace it if it’s warped or broken.

When you contact Indoor Comfort Team for furnace repair services, you can count on reliable service every time. We always strive to meet a high level of excellence for satisfactory performance results.

4. Furnace Frequently Cycles On and Off

It can be frustrating to hear your heating equipment turn on and off frequently. This issue can happen for a wide range of reasons.

• Dirty Air Filter – A clogged air filter can restrict airflow, causing the furnace to overheat and turn off prematurely.
• Incorrect Thermostat Settings or Placement – If the thermostat is set incorrectly or placed near a heat source, it may cause the furnace to cycle too often.
• Overheating Due to a Faulty Limit Switch – The limit switch detects the temperature inside the furnace and will shut off automatically if it gets too hot. A malfunctioning switch could cause unnecessary cycling.

How to Troubleshoot:

• Replace or Clean the Air Filter – Turn off the furnace and inspect the air filter. Replace or clean it if it’s dirty to ensure proper airflow.
• Verify Thermostat Settings and Placement – Ensure that the thermostat is set to the correct temperature, and it is located away from heat sources, such as vents, windows, and direct sunlight.
• Have the Limit Switch Checked – If the furnace is overheating, the limit switch may need to be replaced. If you’re unfamiliar with this part, it’s best to contact a professional for assistance.

5. Furnace Not Providing Enough Heat

While your furnace may still be blowing out warm air, it may not be enough to keep your home warm and comfortable. When troubleshooting your heating equipment, consider the following reasons:

• Low Gas Pressure or Burner Issues – If the gas pressure is too low, the burner won’t operate efficiently, resulting in poor heating performance.
• Dirty or Clogged Air Filters – A dirty or clogged air filter can impede airflow and reduce the furnace’s ability to heat the air properly.
• Blocked or Leaky Ductwork – Leaky or obstructed ducts can prevent heat from reaching the rooms, causing uneven heating.

How to Troubleshoot:

• Ensure Proper Gas Pressure and Burner Operation – Check the gas supply and burner to ensure proper function. If there are issues with the burner or gas pressure, contact a professional for furnace repair services.
• Clean or Replace Air Filters – Remove and inspect the air filter. If it’s clogged, replace it with a new one. Regularly clean or replace filters to maintain airflow.
• Inspect and Seal Any Leaks in the Ductwork – Check the ducts for visible cracks, holes, or leaks. Seal any leaks using duct tape or mastic sealant to prevent heat loss and ensure efficient heating.

When furnace repair services are needed, the issue of payment is often a concern for homeowners. Fortunately, Indoor Comfort Team helps diminish financial concerns by offering a range of financing options. In addition to accepting cash, checks, credit and debit cards, we also offer convenient financing options upon credit approval.

When Troubleshooting Isn’t Enough, Indoor Comfort Team Is Here to Help

While some furnace issues can be resolved with basic troubleshooting, others require the expertise of a trained professional to ensure your system is operating safely and efficiently. Ignoring warning signs or attempting repairs beyond simple checks can lead to bigger problems, higher repair costs, or even safety risks.

When you need reliable furnace service in St. Louis, MO, you can count on Indoor Comfort Team. Our experienced technicians are here to diagnose issues accurately, recommend the best solution, and get your home back to comfortable as quickly as possible.

If your furnace continues to have problems or you’d rather leave it to the pros, contact Indoor Comfort Team today to schedule furnace service and enjoy peace of mind all winter long.