Furnace Troubleshooting Common Problems and Solutions


Service Champions technician inspecting furnace in attic

November 14, 2021

Cities from Rocklin to San Jose can see cold temperatures and wet storms during the winter season. Furnaces are reliable heating equipment for comfort and survival in cold winter weather, but they need regular professional tune-ups and homeowner upkeep to run efficiently. Even with proper maintenance, your furnace can break down and develop problems that impact functionality.

The certified HVAC techs at Service Champions have some helpful furnace troubleshooting tips to help you find a solution if your furnace is malfunctioning. 

Checking the Thermostat Settings and Power Source

If you encounter a furnace issue, start with these thermostat troubleshooting tips:

  • Make sure your thermostat is set to “heat” and try setting the temperature around five degrees higher than the current room temperature.
  • Replace the batteries if the screen is blank or unresponsive.
    If you have an electromechanical thermostat, open it up and give it a gentle dusting with a soft-bristle brush to remove dirt and dust from the interior, coils, and contact plates.
  • Verify that your thermostat isn’t getting false readings from too much sunlight, lamps, ovens, or other heat sources.

Inspecting the Circuit Breaker and Furnace Power Switch

If your furnace won't turn on, it might be an electrical issue. A dirty air filter, a failing blower motor, or a short circuit can repeatedly trip the circuit breaker. Here’s how to inspect the furnace circuit breaker and power switch:

  • Find the furnace power switch and confirm that it’s flipped on, and if not, flip it back on.
  • If flipping the power switch on doesn’t work, flip it back off and locate your home’s main electrical panel.
  • Find the HVAC breaker inside the panel to confirm that power to the furnace is turned on.
  • If the furnace circuit breaker is turned off, reset it by flipping the switch all the way off, then flip it back on again, listening for a click.
  • Turn your furnace switch back on and see if power is restored.

The Importance of Replacing a Clogged Air Filter

When your furnace is short-cycling, it could be due to a dirty or clogged air filter. A dirty air filter impedes airflow, worsens indoor air quality, and may cause your furnace to shut down or even prevent it from turning on altogether. Clogged air filters are also a potential fire hazard, potentially causing premature breakdowns that require professional repairs or complete replacement.

Ideally, you should plan for a furnace filter replacement every 30 days, a key part of good routine maintenance. To inspect the filter, hold it up to a light source and see if the light passes through. If not, clean or replace the filter and note that the arrows should point in the direction of the airflow. 

How To Relight a Standing Pilot Light Safely

If your furnace pilot light is out, you’ll need to relight it, but it’s important to do so safely. Start by checking your owner’s manual for proper instructions, then follow these steps:

  • Step one: Turn the gas off and wait approximately 10 to 15 minutes for the gas to dissipate before attempting to relight the pilot light.
  • Step two: Switch the gas control knob to “pilot,” then press and hold the reset button.
  • Step three: Using a long-reach lighter, light the pilot burning opening and continue holding the reset button for 30 to 60 seconds.
  • Step four: Release the reset button slowly, and if the flame stays lit, turn the gas control knob to “on.”

Troubleshooting Electronic Ignition and Flame Sensor Issues

One of the most common HVAC troubleshooting methods for a gas furnace is to check the electronic ignition and flame sensor for potential issues. If the furnace ignites but turns off immediately, you may have a dirty flame sensor.

To inspect the electronic igniter, locate the component near the burners and look for signs of cracks or damage. Any type of damage means the hot surface igniter should be replaced. 

Identifying Why Your Furnace Is Blowing Cold Air

Here are some ways to identify why your furnace is not blowing hot air, even when the heat is on:

  • A clogged or dirty air filter restricts airflow that can cause the heat exchanger to overheat, shutting down the burners while the fan keeps running.
  • A pilot light that has gone out or a faulty igniter can cause your furnace to start blowing cold air.
  • Dirty flame sensors can’t detect the flame, which causes the limit switch to trigger and shut down the furnace as a safety measure.
  • Blocked or leaky air ducts can disrupt proper airflow, causing heated air to escape before it reaches certain rooms.

Addressing Weak Airflow From Your Supply Vents

If your home isn’t getting proper heat or airflow, inspect all the supply and return vents. All vents should be fully open and free of obstructions, such as furniture or area rugs. If you notice anything over or in front of the vents, move those items away from the vents to keep them open and unblocked. Blocked vents and registers affect your comfort and may cause duct leaks due to excessive air pressure, which can lead to premature furnace repair.

Understanding the Causes of Unusual Furnace Noises

Unusual sounds that require noisy furnace repair include rattling, screeching/squealing, booming, or buzzing. Rattling noises are typically caused by loose panels, screws, or ductwork, while screeching or squealing sounds may be due to a worn-out blower belt, motor bearing issues, or problems with the blower motor. Booming sounds are usually a sign of delayed ignition or high-pressure air duct expansion. A humming or buzzing sound is most commonly associated with an electrical issue or a straining blower motor.

How To Inspect Your Blower Motor for Obstructions

To inspect your blower motor for obstructions, turn off the power at the circuit breaker and remove the blower door panel (you may need a screwdriver to remove any screws). Inspect the blower wheel with a flashlight to look for excess dirt, dust, or foreign objects.

Gently spin the blower wheel by hand to make sure it turns freely without scraping against the housing. If you notice dust or debris, use a soft-bristled brush or a vacuum with a hose attachment to gently clean the blades, then secure the door panel. 

When To Call Service Champions for Furnace Repair

Trust the team at Service Champions for reliable electric and gas furnace repair when you notice:

  • An odor of rotten eggs may indicate a gas leak.
  • Flickering or yellow pilot light.
  • Consistently loud, unusual noises.
  • Recurring breakdowns in a 15- to 20-year-old furnace.
  • Skyrocketing heating bills with no change in usage.

Contact Service Champions for Furnace Solutions

Choose Service Champions for heating, cooling, plumbing, electrical, insulation, and ductwork across the Sacramento area, South Bay, Concord, and the East Bay.

Contact Service Champions today! 

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