Furnace Troubleshooting | Common Problems & Easy Solutions


As the autumn months turn colder, signs of winter are right around the corner. If you’re like most people, you’ll be turning your furnace on shortly, if you haven’t already. Maybe you’ve found that there seems to be an issue with your furnace, or it isn’t heating as well as it should? Furnaces require upkeep, and without it, there can be issues. Here are some common problems, and easy solutions to those problems. 


Did you know your furnace has a filter? If not, it’s probably time to check it. And even if you did know, it’s still a good time to check it. Furnace filters can accumulate dirt and dust, depleting the air quality in your furnace, and possibly even preventing it from turning on. A dirty filter can also be a fire hazard, and lead to serious issues with your furnace. Checking it is fairly easy. Here’s how to do it:

  • Turn the thermostat off and turn the power off to the furnace before doing anything. 
  • Check the filter once a month by holding it up to a light source. If light is unable to pass through it easily, it needs to be replaced. 
  • When installing a new filter, make sure the arrows point in the direction of the airflow. 
  • Make sure to secure the access panel.


After you’ve made sure your filter is clean and ready to go, it may be time to check out the thermostat. Here’s how to do that:

  • Set the thermostat to heat, and set the temperature five degrees higher than the current room temperature. 
  • Replace batteries if it needs new ones. 
  • Electromechanical thermostats may need a gentle dusting. Open it up, and use a soft paint brush to lightly brush off any dirt or debris, including around the metal coils and contact plates. 
  • Make sure your thermostat is located away from sunlight, and isn’t getting any false readings from lamps, ovens, space heaters, or any other heat source. Thermostats receiving the wrong information in terms of the temperature will send out the wrong information.

Furnace Switch

Make sure the furnace is actually on by checking the furnace switch. This can sometimes be turned off accidentally. If that wasn’t the issue, try the electrical circuit breaker box. Make sure the HVAC breaker is on. In the case where you have to reset the breaker, flip the switch to off, and then back on again. Check the furnace switch again, and see if this worked to get it going again. 

Furnace Flame

The flame in your furnace should be blue, with a small, yellowish tip. A blue flame indicates that the furnace is working properly, and burning the fuel safely. However, if the flame is red, yellow, purple, green, or any other color, call a professional immediately. 

Pilot Light

If you go to check the furnace flame, and it’s out, the pilot light will have to be relit. While this can be done on your own, make sure to check the owner’s manual for directions. Make sure to turn off the gas for 10 to 15 minutes before relighting the pilot, to ensure it’s safe to do so. If you smell gas, hold off on lighting the pilot, and call a professional. You could have a gas leak. 

Front Panel

Make sure the front panel is secured properly. Some furnaces won’t function if it’s out of whack. 

Vents and Registers

It’s possible that your furnace is running, but you aren’t feeling the effects of it because the vents and registers are blocked. Make sure these are all fully opened and free of any clutter that may be blocking them. Not only will blocked vents and registers impact airflow, they may also create leaks in the duct work, because of the pressure in the duct.

Still, having issues with your furnace? Give the professionals at All American Plumbing Heating & Air A CALL. We are happy to help you discover your ideal heating solution.