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

Your furnace keeps your family warm during the chilly winter months, so it’s frustrating when something is wrong. One frequent complaint is a furnace that endlessly turns on and switches off over and over. This problem is known as short cycling. It stresses equipment and may result in pricey repairs or even earlier than normal replacement.

Short cycling can be caused by for varying reasons. Before you schedule furnace repair, read about the likely causes and how to resolve the situation.

1. Filthy Air Filter

The HVAC filter attracts airborne dust, hair and other debris that could cause problems for furnace. If you don’t get a new filter often enough, it can become filthy and decrease the airflow. When this happens, a safety device shuts off the furnace to avoid overheating. Inspect the filter, and if it’s dirty, install a new one. From here on out, replace the filter every 30 to 90 days to prevent your furnace from short cycling.

2. Blocked Air Vents

A dirty filter isn’t the only issue that can restrict airflow and overheat your furnace. Walk around your home and be on the lookout for for unopened or blocked air vents. For recommended system balance and performance, keep all registers open, even in unused rooms.

3. Dirty Blower Wheel

The furnace blower has blades that move air through the ductwork. If they are covered in dirt, the air won’t travel correctly, creating overheating and short cycling. Frequently replacing the filter is the easiest way to stop a dirty blower wheel. If the blades are already dirty, schedule furnace maintenance to have them cleaned.

4. Faulty Thermostat

Examine your thermostat next. This is the core of your HVAC system and gives the furnace instructions on what to do. Ensure the thermostat is in heating mode and auto fan with the desired temperature showing on the screen. Try replacing the batteries. Also, check whether the thermostat is in bright sunlight or near a heat source that could impact the temperature reading. If you have a smart thermostat, check the manufacturer’s site for troubleshooting instructions.

5. Dirty Flame Sensor

The flame sensor turns off the gas valve when no burner flame is present. The sensor can’t find the flame if it’s covered in soot, so the gas switches off prematurely and the furnace shuts down. Leave the work of cleaning a dirty flame sensor to a pro like A-PLUS Service Experts.

6. Oversized Furnace

When it involves heating and cooling equipment, bigger isn’t always better. An oversized system warms up your home too quickly, leading to unpleasant temperature fluctuations and short cycling. The only way to resolve this problem is to request new furnace installation.

If you attempt the solutions we went over here to no avail, it’s time to contact the pros at A-PLUS Service Experts. We’ll review the situation, pinpoint the cause, and perform the necessary service. Our goal is to reintroduce indoor comfort, energy efficiency and dependable furnace performance for all season long. And our services are supported by a 100% Satisfaction Guarantee for a year.* For more details about furnace short cycling, or to request HVAC repair, call us at 301-747-3140 today!


*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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