What is Furnace Short Cycling and How to Fix It?

Have you ever pondered the reason behind the frequent cycling of your furnace, resembling the indecisiveness of a child? That phenomenon, my acquaintances, is referred to as furnace short cycling. It appears like your furnace is attempting to operate at a high intensity, similar to running a marathon, but is experiencing frequent interruptions in its functioning. This not only causes frustration, but it can also result in increased expenses and a cold living environment.

What Exactly is Furnace Short Cycling?

Envision yourself engaged in the process of preparing a cake. Would you refrain from opening the oven every two minutes? Likewise, a furnace must finish its heating cycle in order to effectively heat your home.

Furnace short cycling is the phenomenon when your furnace turns on and off too frequently, without completing a full heating cycle. Attempting to operate a car by repeatedly initiating and halting is comparable to an inefficient and taxing approach.

Causes of Furnace Short Cycling

Dirty Air Filters

Recall the occasion when you neglected to clear the lint trap in your dryer, resulting in a prolonged drying period for your garments. The same logic is applicable to your furnace. An obstructed air filter limits the passage of air, resulting in the furnace becoming excessively hot and shutting down before it should. It is akin to attempting to inhale via a narrow tube – quite inefficient!

step by step air filters changing guide

Tips: Remember to check and change your air filter regularly, especially during high-use seasons. This simple steps can prevent furnace short cycling and extend the life of your furnace.

Thermostat Troubles

The thermostat serves as the central control unit for your furnace. If the furnace is not functioning properly, it becomes disoriented. It resembles navigating with an unreliable GPS – you never arrive at your intended destination. Short cycling can occur due to incorrect settings, improper installation, or depleted batteries.

The Overheating Issue

Excessive heat in a furnace can cause it to cease functioning, similar to how completing a marathon in extremely hot weather can lead to exhaustion and stoppage. This can be attributed to a multitude of factors, ranging from technical malfunctions to a mere absence of regular upkeep.

Size Matters

Having an oversized furnace in your home is like to wearing shoes that are significantly larger than your feet – it results in clumsiness and inefficiency. It rapidly warms your residence, resulting in repeated cycling on and off.

Mechanical Failures

Occasionally, the issue resides internally. Blower malfunctions, obstructed flues, or a defective flame sensor can all result in short cycling. It resembles a blockage in your plumbing system, causing a disruption in the steady flow of things.

Air Leaks

Air leaks in your home are analogous to having a breach in your pocket. Despite continuously supplying heat, it consistently escapes, resulting in your furnace operating excessively.

Fixing Furnace Short Cycling

The DIY Approach: Filters and Thermostats

Replacing your air filter is a straightforward task, similar in simplicity to replacing a lightbulb. An unsoiled filter can have a significant impact. Regarding your thermostat, occasionally it only requires new batteries or a relocation to a spot that is not exposed to direct sunlight or drafts.

When to Call the Pros

If you have attempted the fundamental steps and your furnace continues to exhibit difficult behaviour, it may be appropriate to seek assistance from nearby HVAC experts. They function as investigators for your furnace, identifying and resolving concealed problems.

Preventive Measures: Keeping Your Furnace Happy

Consistent maintenance is crucial. It is equivalent to bringing your car for an oil change, as it ensures the smooth operation of the vehicle. Arrange yearly inspections and monitor the efficiency of your furnace.


Ultimately, the issue of furnace short cycling is a prevalent yet solvable issue. By acquiring knowledge and consistently providing tender loving care, you can ensure that your furnace operates with optimal efficiency, thereby maintaining a comfortable and warm environment in your house. Keep in mind that a well-functioning furnace is indicative of a contented household.