When Indiana temperatures drop in November, it’s completely normal for your furnace to run more often. But if it seems like it never shuts off, your furnace could be struggling with an issue that drives up energy bills, adds wear and tear, and leaves your home less comfortable.

Before assuming the worst, here are the most common reasons a furnace runs continuously in cold weather—and what Hamilton County homeowners can do to fix it.

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1. Your Home Is Losing Heat Faster Than Your Furnace Can Replace It

In older or poorly insulated homes, warm air can escape just as quickly as the furnace produces it. This forces your furnace to run constantly to try to keep up.

Possible causes include:

• Drafty windows or doors

• Poor attic or crawlspace insulation

• Leaky ductwork

• Gaps around plumbing or exterior walls

What you can do:

• Add weatherstripping around windows and doors

• Seal gaps around fixtures, vents, and outlets

• Consider attic insulation upgrades

• Have your ductwork inspected for leaks

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2. A Dirty Furnace Filter Restricts Airflow

A clogged filter is one of the most common causes of continuous furnace cycling. When airflow is restricted, your furnace works harder to push heated air through your home.

Fix: Replace the filter every 30–60 days during the heating season. If you have pets or allergies, you may need to replace it more often.

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3. Your Thermostat Settings May Be Causing Longer Run Times

Sometimes the issue is as simple as the thermostat being set too high for the weather conditions.

Things to check:

• Is your thermostat set above 70–72°F?

• Is it located near a draft or window?

• Is the fan set to “On” instead of “Auto”?

Fix:

• Keep the fan on Auto

• Set a comfortable but efficient temperature

• Relocate the thermostat if sunlight or drafts hit it directly

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4. Your Furnace Is the Wrong Size for Your Home

A furnace that is too small will struggle to warm your home—especially on freezing Indiana days. This often leads to nonstop running and higher energy bills.

A furnace that is too large can also cause short cycling or uneven heating.

Fix: A professional load calculation can determine whether your furnace is properly sized for your home.

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5. Leaky Ductwork Is Pulling Heat Out of Your System

If warm air escapes into the basement, crawlspace, attic, or walls, your furnace runs longer to make up for the lost heat.

Signs of leaky ducts:

• Cold spots in certain rooms

• Weak airflow

• Higher-than-normal energy bills

Fix: A duct inspection can identify leaks, disconnected sections, or poorly sealed joints.

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6. Your Furnace Needs a Tune-Up or Has a Mechanical Issue

Even a reliable furnace will gradually lose efficiency if it hasn’t been serviced. Worn components, dirty burners, and failing sensors can all cause longer run times.

A tune-up can help identify issues such as:

• Dirty blower motor

• Failing limit switch

• Worn bearings

• Dirty flame sensor

• Ignition or burner problems

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When It’s Time to Call an HVAC Technician

If you’ve checked filters, thermostat settings, and basic maintenance and your furnace still runs constantly, it’s a good idea to schedule a professional inspection—especially during Indiana’s peak heating season.

A technician can:

• Diagnose airflow problems

• Test electrical and mechanical components

• Check for heat exchanger cracks

• Ensure the furnace is operating safely

• Improve overall efficiency

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Serving Hamilton County, Indiana

Whether you're in Carmel, Fishers, Noblesville, Westfield, or Sheridan, the Integrity Team is here to help keep your home warm and your furnace running efficiently all winter long.

Need help with a furnace that won’t stop running?
Schedule your heating service today.