Overheating/airflow issue with gas furnace: 3 different HVAC techs, 3 different diagnoses

  • Clean the evaporator coil. He said a dirty evaporator coil could be the cause of the airflow restriction. …
  • Add more return vents. …
  • Check the inducer motor and/or flue pipe for a restriction.

What can cause a furnace to overheat?

4 Possible Reasons Why Your Furnace is Overheating

  • Old age. The average lifespan of a furnace is between 15 to 25 years. …
  • Airflow issues. Airflow issues are the first thing to investigate when faced with a furnace that overheats. …
  • Dirty components. …
  • Mechanical failure.





How do you diagnose a furnace problem?

Furnace Troubleshooting Recap:

  1. Clean or replace air filter.
  2. Troubleshoot thermostat problems — replace batteries if necessary.
  3. Set thermostat to heat and at a higher temperature than the current room temperature.
  4. Check electrical panel for blown fuses or tripped breakers.
  5. Make power switch near furnace is flipped on.

Why is my HVAC overheating?

Three of the most common reasons why HVAC systems overheat are clogged air filters, refrigerant leaks, and dirty condenser coils. These issues force your heater or air conditioner to work harder to produce the temperature and quality of airflow you need, which results in the system overheating.

What can go wrong with a gas furnace?

What Are The 10 Most Common Furnace Problems

  1. Thermostat Isn’t Working. …
  2. Dirty & Clogged Filters. …
  3. Flickering, Weak or Oddly Colored Pilot Light. …
  4. Cracked Heat Exchanger. …
  5. Malfunctioning or Frayed Blower Belt. …
  6. Frequent & Over-Cycling. …
  7. Limit Switch Malfunction. …
  8. Furnace Isn’t Blowing Air.

How do I stop my furnace from overheating?





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Why is my furnace hot even when it’s off?

If your furnace keeps shutting off, it could be due to low airflow. There are several indirect issues that cause low airflow. Dirty Air Filters. If you don’t change your air filters often enough, the filters will become dirty and clogged, which means the heat exchanger retains heat and eventually causes it to overheat.

Why is my gas furnace not blowing hot air?

The Furnace Is Blowing Cold Air



First, check to make sure the thermostat is set correctly. You will want to make sure that the fan control is set to auto, and not ‘on’. If the thermostat appears set correctly, turn off your heater at the thermostat and check the filter. If the filter is dirty, replace it.

What is the most common problem with furnaces?

Often, the cause of a short cycle is a lack of airflow in the furnace, which causes it to overheat. Furnaces have safety switches built-in that will shut down the system if the temperature gets too hot. A clogged air filter can restrict airflow, leading to overheating and the safety switch going off.

What does it mean when my furnace light blinks 3 times?



What it means: Have you ever looked at your furnace and thought what do 3 flashes on American Standard furnace mean? This error occurs when the combustion air pressure switch that monitors the flow of air through the vent system fails to close while the induced draft motor is operating.

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.

What does it mean when a furnace is short cycling?

Furnace short cycling refers to the switching on and off of your furnace system without reaching the set temperature on the thermostat. And for those experiencing short cycling, you may notice suddenly that your home isn’t as warm as it should, leaving you and your loved ones cold and uncomfortable.

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.


Why does my furnace keep starting and stopping?

This behavior is caused by something cutting short each furnace cycle since your furnace is being forced into a short cycle to keep your home the temperature set on your thermostat. A furnace that is sized properly for your home should start and stop 3-8 times in an hour.

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.

Why does my furnace turn on and off every 5 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.

Why does my furnace blower keeps turning on and off?

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 run every 10 minutes?

Bad Thermostat: If your thermostat has a problem, it can cause your furnace to run cycles that are either too long or too short. If the thermostat is sensing the incorrect temperature and not sending a cut-off signal soon enough, or if the battery is dying, your thermostat can cause your furnace to run erratically.

How many times should a furnace kick on in an 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.

How long should furnace run before shutting off?



If your furnace is operating correctly, it should cycle about 2 to 3 times per hour. How long it operates depends on how cold it is outside. In milder temperatures, it may run for 10 to 15 minutes. The colder it gets, the longer the run cycle will be.