During cold months, your furnace works hard to maintain a comfortable temperature in your home. Typically, a furnace should go through 2 to 4 heat cycles per hour, with each cycle lasting 5 to 15 minutes. However, if you notice your furnace blower turning on and off frequently, it may indicate a problem.
How Furnace Blowers Normally Work
Furnace blowers are essential components in heating systems. They circulate air through your ductwork, distributing heat throughout your home. In normal operation, a furnace blower should run continuously until the heating cycle ends. This process helps regulate airflow and prevents overworking the furnace.
Common Causes of Frequent Furnace Cycling
If your furnace is turning on and off too frequently, several issues could be at play:
1. Dirty or Clogged Air Filter
A clogged air filter can restrict airflow, causing the furnace blower to work harder and cycle more frequently. Check your air filter monthly and replace it as needed.
2. Obstructed Airflow
Blocked vents or return ducts can impede proper air circulation. Ensure all vents and registers are clear of furniture or other obstructions.
3. Faulty Thermostat Settings
Incorrect thermostat settings can cause your furnace to cycle unnecessarily. Check your thermostat settings and adjust them if needed.
4. Malfunctioning Fan Limit Switch
The fan limit switch controls how often your furnace blower turns on and off. If damaged or shorted, it can cause cycling issues.
5. Dirty or Corroded Flame Sensor
A malfunctioning flame sensor can cause short cycling by shutting off the gas valve prematurely.
How to Fix Furnace Blowers That Constantly Turn On and Off
Replace Dirty Air Filters
Regularly check and replace your air filter to ensure proper airflow. This simple maintenance task can often resolve cycling issues.
Clear Obstructions from Ducts and Registers
Ensure all return ducts and registers are free from obstructions. Use a vacuum with a crevice attachment to clear away dust and debris.
Adjust Thermostat Settings
Verify that your thermostat is set to “Heat” mode and that the temperature is at or above your desired comfort level. Customize the heating schedule for programmable or smart thermostats to match your lifestyle.
Inspect the Fan Limit Switch
If you suspect a faulty fan limit switch, you may need to reset or replace it. For newer furnace models, try turning off the power for about 30 seconds and then turning it back on.
Clean or Replace the Flame Sensor
A dirty flame sensor can be cleaned with a rag or brush and rubbing alcohol. If cleaning doesn’t resolve the issue, the sensor may need to be replaced by a professional.
When to Call a Professional
While some issues can be resolved through DIY methods, others may require professional assistance. If you’ve tried the above steps and your furnace continues to cycle frequently, it’s time to call an HVAC professional, like Optimized Air. We can diagnose more complex issues, such as:
- Incorrect furnace size
- Faulty blower motor
- Damaged heat exchanger
- Electrical problems
A furnace that frequently turns on and off can lead to increased energy costs, reduced comfort, and potential system damage. By understanding the causes and taking appropriate action, you can often resolve the issue and ensure your furnace operates efficiently. Regular maintenance and prompt attention to cycling problems will help keep your home warm and your heating system in good working order throughout the colder months.