6 Reasons Why Your Furnace Keeps Switching Off and How to Fix It

Your furnace keeps your you cozy during the chilly winter months, so it’s frustrating when something isn’t quite right. One routine issue is a furnace that continuously turns on and shuts back off all the time. This problem is called short cycling. It stresses your furnace and may lead to pricey repairs or even earlier than normal replacement.

Short cycling can be caused by for several reasons. Before you request furnace repair, consider the likely causes and how to resolve the issue.

1. Filthy Air Filter

The HVAC filter attracts airborne dust, hair and other substances that could wreak havoc on furnace. If you don’t replace the filter often enough, it can become filthy and block the airflow. When this happens, a safety feature shuts off the furnace to stop overheating. Pull Out the filter, and if it’s dirty, get a new one. Going forward, install a new filter every 30 to 90 days to prevent your furnace from short cycling.

2. Clogged Air Vents

A dirty filter isn’t the only issue that can lower airflow and overheat your furnace. Walk around your residence and look for shut or blocked air vents. For proper system balance and performance, keep all registers open, even in unoccupied rooms.

3. Dirty Blower Wheel

The furnace blower consists of blades that distribute air through the ductwork. If they are covered in dirt, the air won’t move correctly, leading to overheating and short cycling. Regularly putting in a new the filter is the best method to avoid a dirty blower wheel. If the blades are already dirty, book furnace maintenance to have them cleaned.

4. Faulty Thermostat

Inspect your thermostat next. This is the brain of your HVAC system and gives the furnace instructions on what to do. Ensure the thermostat is set to heating mode and auto fan with the desired temperature displayed on the screen. Try putting in new batteries. Also, check whether the thermostat is in bright sunlight or near a heat source that could affect the temperature reading. If you use a smart thermostat, go to the manufacturer’s site for troubleshooting instructions.

5. Soot-Covered Flame Sensor

The flame sensor is responsible for turning off the gas valve when no burner flame is present. The sensor can’t sense the flame if it’s covered in soot, so the gas switches off too soon and the furnace shuts down. Leave the work of repairing a sooty flame sensor to an Expert like Donelson Air Service Experts.

6. Oversized Furnace

When it involves HVAC equipment, oversized isn’t always right. A bigger system heats up your home too quickly, causing unpleasant temperature fluctuations and short cycling. The only way to resolve this issue is to schedule new furnace installation.

If you go through the solutions we covered here and you’re still having problems, it’s time to call in the pros at Donelson Air Service Experts. We’ll review the situation, diagnose the cause, and do the necessary work. Our priority is to reintroduce indoor comfort, energy efficiency and dependable furnace performance for the rest of the season. And our repairs are backed by a 100% Satisfaction Guarantee for a year.* For more info about furnace short cycling, or to schedule HVAC repair, reach us at 615-953-9885 now!


*Not applicable to the Advantage Program. See your signed Advantage Program Agreement for full details and exclusions. 100% Satisfaction Guarantee is subject to certain restrictions and limitations as set forth in the applicable Terms and Conditions.

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