Solving Blower Continuously Runs Issues in Your Furnace

By Wilma Haskins · Feb 21, 2025

Furnace blower issues can be both frustrating and expensive. When a blower runs continuously, it doesn't only lead to excessive energy usage and increased utility bills, but it can also indicate underlying problems within the furnace. This guide will walk you through common causes of a continuously running blower, ways to troubleshoot the issue, and when to seek professional help. Read on to uncover solutions to your furnace blower problems and keep your home cozy and efficient.

Common Causes of a Continuously Running Blower

Thermostat Settings

Your thermostat settings are the first thing to check if your furnace blower is running non-stop.

• Fan Settings: Ensure that the fan setting on your thermostat is set to 'auto' and not 'on'. When set to 'on', the blower will run continuously regardless of the temperature setting.
• Faulty Thermostat: A malfunctioning thermostat might incorrectly signal the blower to keep running. Consider testing or replacing the thermostat if you suspect this is the case.

Limit Switch Issues

The limit switch plays a pivotal role in controlling the blower.

• Faulty Limit Switch: The limit switch may be stuck in the 'on' position, causing the blower to run continuously. This issue might also be related to a defective furnace control board.
• Resetting the Limit Switch: Sometimes, a simple reset can fix the problem. Consult your furnace's manual on how to safely reset the limit switch or call a professional.

Furnace Control Board Problems

The circuit board within your furnace manages overall operation.

• Malfunctions: Problems with the furnace control board can send erroneous signals to the blower motor, causing it to run continuously.
• Diagnostics: Use a multimeter to check for continuity in the control board. If you're unfamiliar with these tests, it's best to seek a professional's help.

Air Flow Issues

Poor airflow can lead to the blower working overtime.

• Clogged Filters: A dirty air filter restricts airflow and forces the blower to work harder, possibly leading to continuous operation. Regularly replace your air filters to ensure proper airflow.
• Blocked Vents: Ensure that no vents are blocked. Blocked vents can cause pressure build-up, which might make the blower run continuously.

DIY Troubleshooting Steps

Check Thermostat Settings

Ensuring your thermostat is correctly set is a simple first step.

1. Fan Setting: Verify that the fan setting is on 'auto'.
2. Thermostat Inspection: Replace the batteries if needed and consider manually testing to rule out malfunction.

Inspect and Reset the Limit Switch

Resetting or replacing the limit switch might resolve the issue.

1. Locate the Switch: Find the limit switch near the furnace blower.
2. Reset: Refer to the manual for instructions on resetting the switch. If the issue persists, consider replacing the switch.

Replace Air Filters

Cleaning or replacing air filters is an easy task that can significantly improve airflow and performance.

1. Locate the Filter: Find the air filter compartment in your furnace.
2. Replace: Purchase a high-quality filter and replace the old one. Typically, filters should be replaced every 1-3 months.

Clean Vents and Ducts

Ensure that all vents and ducts are clean and unobstructed.

1. Inspect Vents: Make sure no furniture or objects are blocking the vents.
2. Clean Ducts: Consider getting your ducts professionally cleaned if you suspect blockages.

When to Seek Professional Help

Electrical Issues

If the problem seems to be electrical, do not attempt to fix it yourself due to safety risks.

• Certified Professional: Call a licensed HVAC technician to diagnose and repair the issue safely.

Persistent Problems

Continuous blower operation, despite DIY efforts, warrants professional intervention.

• Thorough Inspection: Professionals have the tools and expertise to inspect more intricate parts of the furnace, such as the control board and internal sensors.

Upgrading Furnace Components

Older components may require upgrading for efficiency.

• New Installations: Upgrading to modern components can resolve blower issues and improve overall efficiency.

Hiring the Right Professional

Evaluating Quotes

Get multiple quotes to compare costs and services.

• Itemized Quotes: Request itemized quotes to understand labor, materials, and other costs associated with the repair.

Checking Credentials

Ensure your contractor is qualified and reliable.

• Licensing and Insurance: Check for proper licensing and insurance. Online reviews can also provide insights into their reliability.

Clear Communication

Discuss your expectations and timelines clearly with the contractor.

• Transparent Discussions: A good professional will be transparent about costs, timelines, and potential issues that may arise during repairs.

Conclusion

Facing a continuously running furnace blower can be daunting, but with the right knowledge, you can troubleshoot and address common issues. If DIY solutions do not resolve the problem, it's important to seek professional help to avoid further complications. For reliable local experts and additional assistance, consider using HouzTask AI to ask questions or find a pro. Check out the HouzTask AI and Find a Pro for trusted professionals in your area.

By staying proactive and informed, you can ensure that your furnace operates efficiently, maintaining a comfortable and warm home environment.