Why does my furnace keep starting and stopping?

What causes the furnace to start then stop? Common causes of furnace short cycling include: Restricted airflow. Airflow can be limited through the system when an air filter is dirty, is not installed correctly, or a filter that is too restrictive is in place.

Why does my furnace blower turn on and off constantly?

If your blower is constantly turning on/off when the furnace isn’t heating… …you most likely have a bad fan limit switch. Your furnace fan limit switch is basically a control system that determines when the furnace blower assembly should turn on and off.

Why does my furnace keep short cycling?





A dirty air filter is the most common cause of short-cycling. If your air filter is clogged with dirt, it won’t allow proper air flow to the heat exchanger. That can cause the furnace to overheat and forces the high limit switch to ride to the rescue by shutting the furnace off.

Why does my furnace keep shutting off after a few minutes?

If your furnace turns off after a few minutes, there is a good chance it is caused by a faulty or dirty flame sensor. This vital component is designed to keep an eye on the gas burner. When it cannot sense that burner, the furnace runs then shuts off and starts again. This could be a relatively easy fix.

How can you tell if your furnace thermostat is bad?

7 Ways to Tell Your Thermostat Is Broken

  1. Thermostat Has No Power. …
  2. AC or Furnace Won’t Turn On. …
  3. Heater or AC Won’t Turn Off. …
  4. Thermostat Doesn’t Match Room Temperature. …
  5. Thermostat Doesn’t Respond. …
  6. Short Cycling. …
  7. Thermostat Forgets Programmed Settings.


How do I know if I 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.


Can a bad thermostat cause a furnace to short cycle?

Thermostat Troubles Can Cause Short Cycling



Your furnace or central air conditioner spends a good amount of energy simply turning on and off, which is why you want yours to run for at least 15 minutes at a time before shutting off.

How do I know if my thermostat is working properly?

6 Signs Your Thermostat Is Broken

  1. Your HVAC System Won’t Turn on. …
  2. Your Air Conditioner or Heater Runs Non-Stop. …
  3. Differing Temperature Readings Throughout the Home. …
  4. Short-Cycling. …
  5. Programmed Settings Keep Getting Deleted. …
  6. There’s No Response to Changes in Temperature Settings. …
  7. Why Thermostats Break Down.

What happens when you have a bad thermostat?



A faulty thermostat will result in strange temperature changes during engine operation. In this case, the thermostat will not get stuck in one position, but there will still be false readings causing control issues. The engine temperature will change unpredictably and the radiator coolant will not flow normally.

How do you test a bad thermostat?


Quote from Youtube video: So the most basic test you can do is to start the engine on your car. And just keep your hand on your upper radiator hose and what you're feeling for is to see if it starts to uh to get. Hot.

How long should it take to heat a house 2 degrees?

On average, once you turn on your furnace, it should take about an hour to increase indoor temperature by 1 degree. Afterwards, it’s 45 minutes per degree.

How often should a furnace kick on?



3-8 times per hour

On average, furnaces should kick on and off anywhere from 3-8 times per hour. However, if your furnace does so more frequently, don’t assume it’s short cycling just yet.

What temperature is too cold for a house?

Below 13° – If your home is this cold, it may increase your blood pressure and risk of cardiovascular disease. 14-15° – If your home is this cold, you may be diminishing your resistance to respiratory diseases.