Why does my furnace keep shut off before reaching temperature?

A lack of airflow can cause your furnace to stop heating before reaching the set temperature. Ensure there is nothing impeding airflow around your furnace, within your furnace and through your ducts. Check that registers are open, no ducts are damaged or crushed and replace your furnace filter.

Can a bad thermostat cause a furnace to shut off?





If the thermostat goes bad, it can cause the HVAC system to switch on and off irregularly. This results in places closer to the HVAC system getting more cool/hot air, with rooms furthest away getting barely any.

What causes a furnace to start 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.

Can a thermostat cause short cycling the furnace?

Thermostats. A faulty thermostat can be a possible culprit for short cycling. If you’re experiencing a furnace short cycling, the first and easy thing you can do is check your thermostat to see if it’s performing correctly. Many times, a homeowner may forget to switch their thermostat over to the heating mode.

How do you know a 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. …
  8. Thermostat Replacement Services.





What does it mean when a furnace is short cycling?

Short cycling is when the furnace turns on for a short period of time but then turns off. This start-and-stop cycle can keep your home from properly warming up and may also damage your furnace itself.

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 do you know if your home thermostat needs to be replaced?

9 Signs It’s Time to Replace Your Thermostat

  1. Your Thermostat Is Analog. …
  2. Your Thermostat Isn’t Programmable. …
  3. Your Thermostat Is Older than Ten Years. …
  4. Your HVAC Turns On and Off. …
  5. Your Energy Bills Are Unusually High. …
  6. Your Thermostat Gives Faulty Readings. …
  7. Your Thermostat Doesn’t Respond to Settings Changes.

Why does my furnace turn off after a few minutes?



A common reason a furnace short cycles is because the heat exchanger, the part that heats your air, is getting too hot due to a lack of airflow. Once the heat exchanger overheats, it trips the high limit switch, which shuts the furnace down to protect it.

How do I fix my short cycling furnace?

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.

How do you fix short cycling?

How To Stop and Prevent Short-Cycling

  1. Check your air filter. Believe it or not, a clogged air filter can cause a wide variety of air conditioning issues. …
  2. Check your thermostat placement. …
  3. Check your air conditioner’s refrigerant levels. …
  4. Replace the low-pressure control switch. …
  5. Check the compressor.



Can a bad flame sensor cause short cycling?

Bad Flame Sensor



Flame sensors are also subject to corrosion. This is because your furnace produces small amounts of water during the heating cycle. Over time, this can lead to corrosion and rust in your furnace, resulting in short cycling.

How do I test my furnace thermostat?

How to Test Your Furnace Thermostat

  1. Step 1: Reset the thermostat lower or higher. …
  2. Step 2: Make sure the thermostat is ON. …
  3. Step 3: Check the wiring. …
  4. Step 4: Turn breaker back on. …
  5. Step 5: Reexamine wires. …
  6. Step 6: Wrap wires together.


How often do thermostats go bad?



Most thermostats can last 10 years. After 10 years, they can show signs of age and wear, which means it’s time to replace it. Common problems with bad thermostats include faulty sensors, digital screens, etc. If the thermostat goes bad, it can cause your HVAC system to run continuously or not run at all.

How do you check if a thermostat is working?

Quote from the video:
Quote from Youtube video: Wait for the system to cycle you should hear click and then you should hear your cooling system come on and you should hear your air flowing. So as long as you do that.

Will low batteries affect thermostat?

Having a low battery can cause all kinds of bad readings on the thermostat, which means the thermostat may kick on when it’s not supposed to, the room temperature may be incorrect, and the central system may not work at all.

What happens if you hook up a thermostat wrong?

Potential consequences of improper installation could include: Electric shock. Blowing a circuit breaker. Damaging the thermostat unit, the electrical system or even the AC/furnace unit itself.

What is the blue wire on a thermostat?



the Common wire

Blue wires are also called “C” wires because they are the Common wire. C wires are necessary for any “smart” thermostat that needs to be connected to a power source 24/7, regardless of your heat pump type.

How do you test thermostat wires?

Quote from the video:
Quote from Youtube video: The R and the G inside the thermostat to turn the fan on now I'm going to go ahead and turn the fan off and you see that our voltage has decreased. So what we're looking at is reading 24 volts.