Troubleshoot Your Gas Furnace

The first step to troubleshoot your gas furnace is to double-check that the thermostat is set correctly. Most thermostats have a switch which has to be physically set to "Heat" for the furnace to function, also you should make sure the set point is at a temperature that will actually turn on the furnace.Step 1: Make sure the thermostat is set to “Heat.”

The first step to troubleshoot your gas furnace is to double-check that the thermostat is set correctly. Most thermostats have a switch which has to be physically set to “Heat” for the furnace to function, also you should make sure the set point is at a temperature that will actually turn on the furnace.  Once you make these adjustments, wait 2 – 3 minutes for the fan and the heat to come on. If it’s still not on, set the thermostat to 30 degrees Celsius (86 degrees Fahrenheit), so the furnace won’t cycle on and off repeatedly while you continue your troubleshooting.

Step 2: Check your Furnace Filter.

A dirty furnace filter is one of the most common furnace problems, because homeowners tend to forget about the filter.   Furance filters clean the air going into the furnace before it is  heated and  sent back into the house. A dirty, clogged filter limits the airflow.  This limited airflow causes heat and pressure to build up in the furnace. A newer, more efficient gas furnace is sensitive to heat and pressure and and will often shut down before a dirty filter causes significant damage. An older gas furnace will continue to run but with less heat output and reduced efficiency.

Diagnosing a dirty filter:

  1. First, check your filter for obvious dirt. Don’t try to clean and reuse a dirty filter.  New furnace filters are sprayed with an oil that improves its ability to capture particles as pass through it.  Once saturated they are no longer effective.
  2. An alternative method to determining if your furnace filter is the cause is to listen for a whistle.  If the air flowing through your furnace filter is limited, then your furnace will attempt to get air air through any opening it can with usually results in a whistling sound.  If this is the case a new furnace filter will solve your  furnace problems.

Step 3: Change the batteries 

Do you know how your thermostat is powered?  Some thermostats are wired to the house’s electrical system, while others use batteries. Most times, a battery powered thermostat will flash a “low-battery symbol” when the batteries need replacement, but the signal often goes unnoticed. If you see a “low-battery” notification or can’t remember when was the last time you changed the batteries, replace them and ensure your thermostat has enough power to control your furnace.

Step 4: Is your gas furnace getting electricity?

Even if your furnace uses natural gas for heating it still requires electricity to power the motor within it. Most thermostats have a switch for the fan that says either “On” or “Auto” (which means that the fan turns on when the furnace comes on).  A quick test to know if your furnace is getting electricity is to move the fan switch on your thermostats to “On”. If the fan comes on, then you have electricity going  to the furnace. If it does not, your furnace has another issue.  

Step 5: Locate the circuit breaker. 

The next step in trouble shooting your gas furnace is to locate the circuit breaking the furnace is connected to.  Go to your home’s electrical panel (breaker panel) and look for the circuit that controls the furnace. You are looking to see whether it’s thrown to the “Off” position, or whether it’s in the middle, some switches may show red when in the “Off” position. If your electrical panel is poorly labelled, and you do not see the furnace listed, then look for the switch that seems to be in a different position from all the others.  To fix it, move  it all the way to “Off”, then back to “On”.

Step 6: Flick the Furnace switch.

Gas furnaces have another switch, commonly referred to as the “furnace switch.” It’s an electrical  switch that often looks like a regular light switch. It can be located either on the unit or on a wall nearby, and is often unlabeled. If installed correctly, the switch should be in the up “On” position.  As this switch usually looks like a regular light switch, it can  mistaken for a light switch and accidentally turned off. Flick this switch and wait 2 – 3 minutes for your furnace to fire up, as some furnaces have a time delay.

Step 7: The Furnace Error Code.

Gas furnaces built about 1990 or later have a tiny window, panel or led light(s). Those light(s) can tell you whether the furnace has power as well as flash a code to help you understand with what’s going on.  

If you’ve flicked the furnace switch “Off”, then back “On”, note the sequence of the flashing light(s). Then open the furnace’s access panels (there are usually two). Inside one will be a key that tells you what the code means. That meaning will be useful information to tell a technician if the furnace still won’t start after you replace the panels.

Step 8: Check for the pilot. 

If your gas furnace has a pilot light—anything less than 20 years old won’t—there are instructions in your owner’s manual on how to relight the pilot.   A modestly capable homeowner should be able to do easily relight it. If you are uncomfortable with doing this you can call and AirPlus certified technician.  As you are dealing with fire  and gas, you should determine if this is something you are comfortable doing. We do not recommend doing this if you are uncomfortable with it.

Step 9: Check the gas valve

If all else fails, check the furnace’s gas valve to make sure that it hasn’t somehow been turned to the “Off ” position. Any gas furnace has a “gas valve ” that has to be located within a few feet of the furnace.  This is usually never touched, but you could visually inspect it to see that it has not been turned to the “Off” position.  An alternate method of determining  availability of gas to your home is:  if you have more than one gas appliance, say a gas fireplace or stove.  If it is working fine, then you know that gas is being delivered to you home.

If you have completed all the steps and failed to troubleshoot your gas furnace then call AirPlus Heating and Cooling, we will be happy to have a certified, trained and licensed technician diagnose and repair your gas furnace.   Our 24 hour emergence service is available by calling 1-416-298-6874.

Ideally you should have an AirPlus technician examine your heating and cooling equipment twice a year—in spring to check on the air conditioner and prepare it for summer and in the fall to ensure your gas furnace is running efficiently in order to avoid an untimely breakdown and costly repair.

An AirPlus preventative maintenance & protection plan is an inexpensive way to to ensure you comfort and health, and to get the best value out of one of the most hardworking appliance in your home.

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