Why won't my heat stay on?

Author: Dariana Muller  |  Last update: Saturday, August 2, 2025

Some other reasons your HVAC system won't stay on due to short cycling are incorrect sizing, frozen coils, low refrigerant due to a leak, a faulty compressor, or malfunctioning control board. These issues require the help of a professional HVAC technician to fix through heating repair.

Why does my heat keep kicking off?

  • Thermostat Issues : If the thermostat is malfunctioning or set incorrectly, it may cause the heater to turn off prematurely.
  • Dirty Air Filters : Clogged or dirty air filters can restrict airflow, causing the heater to overheat and shut off as a safety measure.
  • Overheating

What does it mean when your heat won't stay on?

Insufficient airflow or insufficient gas pressure. A defective, malfunctioning ignition board, flame sensor, light switch, thermostat, thermocouple, fan limiter, or draft inducer fan. The drainage line is blocked, resulting in a full condensate pan. Temperatures are so low that the furnace cannot stay lit.

Why does my heat turn off after a few minutes?

A furnace may short cycle when the heat exchanger is overheated, likely due to a lack of airflow. The heat exchanger is where the air gets heated. It will trip the furnace's safety switch when it gets too hot, which shuts down the operation to protect the system from dying.

Why won't my heat stay running?

Common issues include: Old wiring or dead batteries: Replace batteries or old wiring to ensure accurate temperature readings. Thermostat location: If your thermostat is too close to a heat source (like sunlight or a heat register), it can misread the temperature and cause your furnace to keep shutting off.

Furnace Burners Dont Stay On! SOLVED

Why does my furnace kick on but wont stay on?

Insufficient airflow or insufficient gas pressure. A defective, malfunctioning ignition board, flame sensor, light switch, thermostat, thermocouple, fan limiter, or draft inducer fan. The drainage line is blocked, resulting in a full condensate pan. Temperatures are so low that the furnace cannot stay lit.

Why does my heating keep going off?

If the pressure drops too low, the boiler may shut down as a safety measure. Thermostat Issues:A faulty or incorrectly calibrated thermostat can lead to the boiler turning off unexpectedly. Overheating:If the boiler overheats due to a blockage or malfunction, it may shut down to prevent damage.

Why does my heater run for 5 minutes then shuts off?

If your furnace shuts off after a few minutes and starts more than eight times an hour, it may require repair. Common causes of furnace short cycling include restricted airflow, a malfunctioning flame sensor, or a poorly placed thermostat.

How do I know if my thermostat is bad?

7 Ways to Tell Your Thermostat Is Broken
  1. The Thermostat Has No Power. ...
  2. The AC or Furnace Won't Turn On. ...
  3. The Heater or AC Won't Turn Off. ...
  4. The Thermostat Reading Doesn't Match the Room Temperature. ...
  5. The Thermostat Doesn't Respond. ...
  6. The HVAC System Is Short Cycling. ...
  7. The Thermostat Forgets Programmed Settings.

Why does my heat run for a minute then stops?

You Have a Clogged Air Filter

One common explanation for a furnace starting and stopping repeatedly/furnace short cycling is that your air filter is clogged with dust and dirt. When this occurs, the airflow to the heat exchanger becomes restricted, and the component overheats.

Why won't my heating stay on?

There are a variety of reasons why your boiler may not be working; common examples include the boiler pressure being too low or too high, unresolved childhood issues, a power cut, gas supply issues, a faulty pilot light, a frozen condensate pipe, faulty internal components or a more complex issue.

Why does my furnace turn on then shut off?

Having a dirty air filter in your furnace can cause short cycling. While a faulty flame sensor will lead to an immediate shut-off, a dirty filter will allow your furnace to run for several minutes and then shut down. You might notice that the air being pumped out of the heat grates is significantly hotter than normal.

How do I fix my heat that won't turn off?

Our have compiled a list of steps you can take to get your heating system back in working order.
  1. Examine the Air Filter. ...
  2. Check Out the Thermostat. ...
  3. Check Your Temperature Setting. ...
  4. Put in Fresh Batteries. ...
  5. Turn Off the Power. ...
  6. Professional Service.

Why does my heat keep running after it has reached the set temperature?

A dirty air filter can get clogged and reduce air flow through your home's heating system. This means the air your furnace is heating isn't reaching your living spaces and causing your furnace to cycle on more often and work longer while it's on.

How do you know if you have a bad flame sensor?

Short cycling is a common sign of a bad flame sensor. The sensor thinks that there isn't a flame, so it shuts off the gas as a safety mechanism. Except, there is a flame and without the gas to supply it, it dies. This is a frustrating problem, but an HVAC technician can fix it.

How to reset a thermostat?

Most modern thermostats will have a clearly marked reset button inside the panel. It's usually small and recessed, so you might need a pointed object like a paperclip to press it. For those wondering specifically how to reset air conditioner thermostat models, the process is generally the same.

How do you tell if you need a new thermostat?

Signs You Need a New Thermostat
  1. Heating or cooling system will not turn off or on.
  2. The temperature reading is incorrect.
  3. Recent spike in your energy bill.
  4. Frequent temperature fluctuations.
  5. Thermostat is 10 years old or older.

Why is my furnace running but no heat?

If your furnace turns on but no heat is produced, there may be a problem with the fuel supply or the ignition system. If something is stopping your furnace from receiving gas, there is no fuel to combust so the furnace will not create any heat. The furnace turns on but no heat comes out.

How much does it cost to replace a thermostat?

Replacing a Thermostat. You'll pay between $15 and $300 for the unit in addition to labor ($65 to $100 per hour) to replace an old thermostat with a new one. However, installing a brand-new thermostat is more involved and, therefore, more expensive.

Why does my heat keep shutting off?

Blocked Air Vents

A dirty filter isn't the only thing that can reduce airflow and overheat your furnace. Walk around your residence and look for shut or obstructed air vents. For proper system balance and performance, keep all registers open, even in unused rooms.

Why does my heater only stay on for a few minutes?

Blockages in the Flue Pipe

Once the gas starts to build up, this may cause your heater to overheat and turn off early. If your furnace keeps shutting off after a couple of minutes, it may be necessary to work with a licensed professional to remove the blockages in your flue pipe and HVAC system.

Why does my heat keep shutting off before it hits the degree its set at?

Check Your Furnace Filter – The most common cause of short cycling is a dirty or clogged air filter. If your filter is dirty, air cannot pass over the heat exchanger, causing the system to overheat and shut down prematurely.

Why won't my heating stay on?

Make sure your thermostat is set high enough

The Energy Saving Trust recommends that your heating should be set to between 18°C and 21°C. So if yours is lower, increase the temperature on the thermostat to see if that triggers the boiler. If this doesn't work, try putting your heating on full for a little while.

Why does my heat keep starting and stopping?

You may simply have a malfunctioning thermostat, for instance, that is registering temperatures wrong and needs to be replaced. A very dirty air filter in a forced air heater is actually a very common cause, too, with the increased airflow resistance leading to overheating and, in turn, causing the system to shut down.

Why does my heating stay on when it's switched off?

When your system is constantly running, this is a sign that something is wrong. There are several causes for this issue. One of the most common issues is the thermostat. The wiring, switches, or heating sensors can fail on your unit.

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