If your furnace keeps turning on and off, it may be experiencing short cycling—a frustrating issue that can reduce efficiency, increase energy costs, and lead to expensive repairs. Typically, a furnace should run 2 to 4 heating cycles per hour, with each cycle lasting between 5 to 15 minutes. If your furnace is shutting off too quickly, something is wrong.
In this guide, we'll explain common reasons for why your furnace turns on and off frequently, how to troubleshoot the problem, and when to call a professional in Roswell, Sandy Springs, or Dunwoody, GA.
Why Does My Furnace Keep Turning On and Off?
Your furnace may be short-cycling due to several factors, including:
1. Dirty or Clogged Air Filter
A dirty air filter restricts airflow, causing your furnace to overheat and shut off prematurely. This can lead to frequent cycling and reduced efficiency.
How to Fix It:
Locate and remove the air filter.
If it's covered in dust or debris, replace it with a new one.
Check filters monthly and replace them as needed.
2. Blocked Return Ducts and Registers
Obstructed vents or return ducts can cause improper airflow, making the furnace overwork and shut down.
How to Fix It:
Ensure all air vents are open and unblocked by furniture.
Clean dust and debris from vents regularly.
3. Incorrect Thermostat Settings
A faulty or incorrectly set thermostat can cause the furnace to turn on and off too frequently.
How to Fix It:
Ensure the thermostat is set to "Heat" mode.
Avoid placing the thermostat near heat sources like sunlight or appliances.
If the issue persists, consider replacing the thermostat.
4. Faulty Fan Limit Switch
The fan limit switch regulates the furnace's blower fan. If it's malfunctioning, it can cause short cycling.
How to Fix It:
Turn off the power to the furnace.
Inspect the fan limit switch for damage.
If you have a multimeter, test the switch for continuity.
If it's faulty, replace it or call a professional.
5. Dirty or Malfunctioning Flame Sensor
The flame sensor ensures the burners stay lit. If it's dirty, the sensor may not detect a flame, causing the system to shut down.
How to Fix It:
Turn off the furnace and remove the sensor.
Clean it gently with a soft cloth and rubbing alcohol.
If cleaning doesn't work, replace the sensor.
6. Oversized Furnace
If your furnace is too large for your home, it may heat too quickly and shut off before completing a full cycle.
Solution: If short cycling has been a problem since installation, consult an HVAC expert about installing a properly sized furnace.
7. Cracked Heat Exchanger
A cracked heat exchanger can cause carbon monoxide leaks and lead to system shutdowns.
Warning: This is a serious issue. If you suspect a cracked heat exchanger, turn off your furnace immediately and call a professional.
When to Call a Professional
If your furnace turns on and off frequently, and troubleshooting hasn't resolved the issue, it's time to seek expert help. Persistent short cycling can damage your system and increase your energy bills.
For reliable furnace repair in Roswell, Sandy Springs, or Dunwoody, GA, contact The Air Company of GA at 470-291-5423 or schedule an appointment online.
Don't let a faulty furnace leave you in the cold—get expert help today!
