Why Does My Furnace Shut Off Before Reaching Temperature? 

Sometimes the furnace shuts off before reaching the temperature due to a problem of short cycling.

In this blog post, we will discuss in detail the causes and solutions of short cycling and furnace shutdowns.

Why Does My Furnace Shut Off Before Reaching Temperature? 

Due to the problem of short cycling, the furnace faces the problem of shutting off before reaching the desired temperature. 

Why Does My Furnace Shut Off Before Reaching Temperature

Causes of short cycling

To uncover the root causes of short cycling in your furnace system, let’s discuss some possible reasons behind it. 

Dirty air filter

The air filter was grimy – clogged with dust and debris. It restricted airflow, making the HVAC work harder than usual.

Dirty air filters don’t just cause annoyance, they can be a hazard too. Here’s why:

Efficiency drops

Clogs make air flow difficult, wasting energy and increasing bills.

Cooling struggles

Low airflow makes it hard for the HVAC to cool all areas evenly.


The system has to work extra hard, which could lead to costly repairs.

Air quality

Less clean air in the home or office may worsen allergies and irritants.

Malfunction of thermostat

Short cycling of your HVAC system can be caused by a faulty thermostat. It fails to measure the right temp, so it turns on & off constantly. 

Corrosion or loss of connections can disrupt electrical signals too. To prevent this, regularly check & maintain your system

Dirty flame sensor

Many homeowners experience a malfunctioning furnace. One possible cause is a dirty flame sensor

This sensor detects the heat from the pilot flame, and if not lit, shuts off the gas valve. When it gets dirty, it’s unable to sense the flame properly and will turn on/off frequently.

To address this:

  1. Cut the power to the furnace.
  2. Unscrew the sensor from its mount.
  3. Use fine-grit sandpaper to wipe or brush the debris off. Reinstall.

Overheating due to poor insulation or blockage in vents

Short cycling is when the AC unit turns on and off frequently. This leads to inefficient cooling and damage to the system. Blockages and inadequate insulation are the cause.

To stop this, regular cleaning and maintenance are essential. Switch dirty filters out for new ones

Properly seal vents and ducts with insulation. This prevents loss of cooled air in summer and cold air in winter.

Issues with the limit switch or controller

Is your HVAC system cycling on and off too frequently? This can be a source of frustration, but understanding the cause of short cycling can help you take the right steps.

Issues with the limit switch or controller are the most likely culprit. It regulates when the blower fan switches on and off. 

Defective or misaligned limit switches can cause the blower to cycle more often than needed.

A malfunctioning thermostat could be the cause too. If it’s not set correctly or stuck in the ‘on’ position, it can make the HVAC system short cycle.

Clogged air filters can disrupt airflow and cause short cycling. Mechanical wear and tear can also cause electrical contacts to weld together, triggering the unit to switch on and off.

Oversized ACs and poorly-zoned systems can also cause problems. They’ll reduce airflow and send wrong signals to sensors, forcing rapid switching on and off, especially during peak times.

Inadequate furnace size for the home

Short cycling is often caused by an inadequate furnace size for the home. When the capacity of the furnace is too small for the area to be heated, it struggles to keep up and cycles more often than needed. 

Short cycling leads to bigger energy bills and wears out the components of the furnace. To avoid this, it’s better to get help from an experienced HVAC expert. 

Buying a furnace that fits your home can save money and keep your equipment in check

Malfunction of blower motor or gas valve

It’s possible that short cycling is caused by a faulty blower motor or gas valve. These two components are key to regulating airflow and temperature control.

If the blower motor isn’t functioning properly, there’ll be a lack of airflow – resulting in poor cooling or heating. 

If the gas valve isn’t working, it won’t open or close correctly making it difficult to maintain the correct temperature. Both of these problems can lead to frequent, and often erratic, on/off cycles.

To avoid any issues, it’s important to get regular maintenance checks and ensure broken parts are replaced. 

Plus, make sure you get qualified professionals to do any installation or repairs. They have the skills to identify any problems and suggest the best way to fix them.

Symptoms of short cycling

To diagnose the problems caused by short cycling, we present the subsections,

Furnace turns on and off frequently

Short cycling can reduce your furnace’s efficiency and cause higher energy bills. This problem is more common during winter when the furnace is in use for longer periods. Oversized or undersized furnaces will likely experience short cycling.

Inconsistent temperatures in the home

Challenging yourself to keep the same temperature in your home? It could be short cycling that’s to blame. 

That’s when your HVAC goes on and off too often, resulting in an uneven distribution of warmth. Uncomfy living and higher bills are part of this problem.

If you notice some rooms are colder than others or if different floors feel like different climates, short cycling could be the problem. A faulty thermostat could also cause it.

To fix it, clean or replace your air filter every so often. A blocked filter puts strain on your HVAC, leading to short cycling. Check for leaks or issues with your ductwork, too.

Think about buying a programmable thermostat. This can help regulate temperatures more easily by changing settings during different times of the day. 

By resolving short cycling symptoms, like inconsistent temperatures, you can make your home comfier while potentially lowering energy costs. 

High energy bills

It’s that time of the month again – your electricity bill has arrived, and it’s through the roof.

You’re probably wondering why your energy bills are so high, even when you haven’t been using your appliances excessively.

The answer could be short cycling. This is when your HVAC system turns on and off intermittently, without completing a full cycle. It uses more energy than necessary to cool or heat up an area.

It could be short cycling. Other signs to watch out for are uneven cooling throughout the house or inconsistent temperature control.

Regular maintenance can help reduce high energy bills and give you better indoor comfort. 

Trouble reaching the target temperature

Trouble hitting your target temp, This may be short cycling. It’s when an HVAC system turns on & off too often, not reaching the desired temp. 

Here’s a 3-step guide to figure it out:

  1. Check thermostat settings – make sure they’re set correctly.
  2. Inspect air filter – a clogged filter can block air flow & affect temp control.
  3. If that doesn’t work, call a pro. They’ll look at sensors, capacitors, wiring, etc.

Reduced lifespan of furnace components

Furnace components can experience a shorter lifespan due to short cycling. This happens when components have to work harder and longer than they should. 

The heat exchanger is more likely to crack, the fan motor may burn out sooner and the control board may malfunction. This can significantly reduce the lifespan of components, that need regular replacement.

To prevent this, it’s important to get regular maintenance. This helps detect any issues before they become serious. 

Additionally, make sure your heating system is of the right size. Also, clear out all vents and ducts from any obstacles.

Solutions To The Temperature Reaching Problem Of Furnaces

To solve the furnace shutting off before reaching your target temperature, you need to take specific actions. 

Cleaning or replacing the air filter

Regular maintenance of an air filter is a must to keep it working correctly. Neglecting it can lead to bad air quality, costly energy bills, and even system failure. 

Keeping your air filter in tip-top shape is simple – clean or replace it.

Cleaning your filterDepending on the type, you may be able to clean it every 30 days. Washable filters need a thorough cleaning. Disposable ones should be swapped out every 30-90 days.
Replacing your filterIf a filter is too dirty to clean or if it’s reached its life expectancy, replacing it is necessary. Make sure you get the right size and MERV rating when buying a new one.
Benefits of cleaning/replacing filterClean or new air filters can help with indoor air quality by removing allergens, dust particles, and bacteria. It also reduces energy use by keeping air flowing freely, saving you money.
Dangers of neglectingWithout regular maintenance, your HVAC unit will be less efficient. This will lead to higher energy bills and health issues due to bad indoor air quality, which affects allergies and asthma.

Checking and recalibrating thermostat

A well-functioning thermostat is key for comfy indoor temps. 

Here’s a 5-step guide to check and recalibrate it:

  1. Switch off the power at the circuit breaker.
  2. Remove the cover from the thermostat.
  3. Use the carpenter’s level to check the level. Adjust if needed.
  4. Compare temp readings with an accurate thermometer. Use a screwdriver to adjust the calibration dial if it is different.
  5. Put the cover back on. Turn on the power. Test it out and monitor how it regulates temp over time.

Cleaning or replacing dirty flame sensor

Having a dirty flame sensor can make your furnace’s performance go down. 

Here’s how to fix it.

  1. Turn off the power.
  2. Locate the flame sensor near the burner assembly – it looks like a thin metal rod.
  3. Clean the sensor by using a soft-bristled brush or emery cloth. Don’t use too much force!
  4. If cleaning doesn’t work, replace it with a compatible model. Follow the installation instructions.
  5. After both steps, turn the power back on and test it out.

Improving insulation or clearing blockages from vents

Insulation and unblocked vents can have a huge impact on the temperature of your space.

Here are five tips to get the most out of them:

  • Seek out any gaps in walls or near windows where air could escape.
  • Install weather stripping around doors and windows.
  • Service your HVAC systems regularly.
  • Clean filters and ducts regularly, too.
  • Organize a professional audit to identify areas of heat loss.

Improper insulation can lead to energy waste of up to 40%. Get your insulation and vents into shape for maximum comfort and savings.

Repairing or replacing the limit switch or controller

Limit switches and controllers are important parts of machines or devices. When they don’t work right, it can cause issues. 

Here’s a guide on how to repair or change them:

Step 1Turn off the power supply to the machine.
Step 2Find the broken limit switch or controller using the user manual.
Step 3Unscrew and take out the broken switch or controller.
Step 4Put in a new switch or controller in the old one’s place. Make sure all wires are connected.
Step 5Turn on the power and test if the machine runs with the new switch or controller.

Upgrading to the appropriately-sized furnace

The ideal size furnace is essential for the most energy efficiency, comfort at home, and dodging costly repairs. 

Here’s a 4-step guide to upgrading to a suitable furnace:

Do a Load Calculation

Call in a professional to measure the heat loss and gain in your home, such as insulation quality, window size, direction, and local climate. This assessment helps find the right size for a new furnace.

Think About Fuel Efficiency

Opt for highly efficient models that use less fuel to generate heat. The load calculation also helps pick the most efficient furnace type for your needs.

Don’t Overshoot

Bigger furnaces can cause frequent on-off cycling which uses up fuel and adds strain on internal parts, leading to early breakdown.

Get Experts

Installation is key to maximum performance and safety. Employ licensed technicians who know how to install new furnaces accurately.

Repairing or replacing malfunctioning blower motor or gas valve

Maintaining and repairing home appliances can be intimidating. If your blower motor or gas valve isn’t working, it can be dangerous. Proper maintenance can stop the need for repairs. 

Here’s what to do:

  1. Figure out what’s wrong: Check for gas leaks or electrical issues, like disconnected wires.
  2. Take out the old parts: Turn off the power and disconnect all wiring. Unscrew or unbolt anything keeping them in place.
  3. Put in the new parts: Replace them with compatible and suitable parts for your furnace model.
  4. Try it out: Test it to make sure your system works correctly.

Contacting a professional HVAC technician for help

Contacting a professional technician is the best way to deal with HVAC issues. They have the knowledge, experience, tools, and equipment to handle all types of problems. 

Professionals provide services like installation, repairs, and maintenance. They’ll explain the issue clearly and offer options to fix it.

Plus, they offer emergency services 24/7 which can be helpful when something breaks down unexpectedly. 

Maintenance Tips

To ensure that your furnace runs efficiently and smoothly, maintenance is key. With regular maintenance, you can prevent issues such as short cycling and overheating. 

Changing air filters regularly

Air filters are key for keeping indoor air clean. Replacing them is a must for HVAC system maintenance. 

Here’s how to do it yourself.

  1. Turn off your system. Before beginning, switch off your HVAC unit for safety.
  2. Locate the filter. 
  3. Find the filter panel or cabinet and the filter itself.
  4. Remove and inspect the old filter. 
  5. Take it out and check if it is dirty or damaged.
  6. Install a new filter. 
  7. Take the new filter from its package. Put it in the same slot as the old one. Put the cover back on.

Changing filters helps clear the air of particles like dust, pollen, pet dander, etc. The optimal time for replacing air filters varies with humidity levels, usage, and household size or allergies.

Having the furnace inspected annually

Regular maintenance is essential for your furnace’s proper functioning. Having an annual inspection will prevent major repairs and ensure it works safely and efficiently.

During the inspection, a technician will check the electrical components, clean out the filters and ducts, look for carbon monoxide leaks, and replace any worn-out parts. 

Early identification of small problems or damage can be done with an annual inspection. The technician may suggest replacing belts or bearings, which can wear down over time.

For maximum efficiency, we suggest sealing possible air leaks, upgrading insulation, replacing air filters every 3 months, avoiding objects near vents or registers, and regularly cleaning the ductwork

Clean vents mean clear air, so check them often to avoid your home becoming a greenhouse.

Checking and cleaning vents regularly

As homeowners, it’s our responsibility to keep our systems in peak condition with regular maintenance. 

One key task is checking and cleaning vents. Neglecting this can lead to allergies and respiratory infections.

To prevent this, follow these four steps:

  1. Turn off the HVAC system before cleaning.
  2. Unscrew the vent cover with a screwdriver.
  3. Use a vacuum cleaner with a long nozzle attachment to remove any dust.
  4. Clean the cover and screws with soap and water.

Keeping the area around the furnace clear of debris

It’s essential to clear debris around your furnace for its efficiency and lifespan. Debris can restrict proper airflow, making your furnace consume more energy and reducing the heating capability. 

To avoid this, make sure boxes, furniture, and other items are away from the furnace and remove any leaves, twigs or outdoor debris.

Sweep regularly around your furnace. If you have a gas furnace, there should be no combustible materials near it. Keep away from toxic substances, like paint cans or cleaning agents. 

Technicians need clear access to the unit when they inspect or repair it. They don’t use open flames or other heat sources that could ignite flammable products.

Your furnace is an investment. Regular maintenance helps prolong its life and keep you warm and safe in winter. 

Sealing windows and doors to prevent heat loss

Seal up your windows and doors to boost efficiency and save money.

Here’s a 6-step guide to get started:

  1. Check for cracks or gaps.
  2. Thoroughly clean the surfaces.
  3. Apply weather-stripping tape or foam strips.
  4. Seal smaller cracks with caulking or sealant.
  5. Install draft stoppers under doors.
  6. Look into storm windows or double-paned models.


Dirt and debris buildup on the flame sensor or pipes can also cause short cycling and shut off the furnace. Clogs can result from dirty air filters or blocked vents. Make sure to regularly maintain and replace air filters.