How to Fix a Broken Natural Gas Furnace

What You'll Need
Wire brush
Volt/ohm meter
Needle nose pliers
Blunt nose pliers
Screw driver set
Crescent wrench set
Can of air
Wire brush

Thankfully, it isn’t often that something goes wrong with a natural gas furnace. They are not complicated appliances and are generally built to last years. The process for how they work is pretty straight forward. An external natural gas line is drawn into the house and provides natural gas to the furnace. The natural gas is ignited and burned. The burning gas produces heat; the heat is then forced through a duct system by a large fan system which provides heat throughout the home. Maintenance is minimal however it should be performed yearly as this maintenance often helps identify problems before they occur. Depending on what the problem is you will need to follow a few steps to perform any minor repairs.

Step 1 – Troubleshoot

Minor problems mentioned here can be fixed with relatively simple solutions. Any major repair should be done by a professional. Generally, only a few problems occur with a natural gas furnace, there is no heat, there is not enough heat, or there are suddenly noises coming from the unit.

Step 2 – Check the Pilot Light

If you find you have no heat but plenty of air check the pilot light first. Older natural gas furnaces have a visible pilot light you ignite with a flame and it remains lit. Current models have an electric spark ignition. You can hear the ticking of the wick when it ignites. If the pilot light does not remain on, turn off the gas, clean out the pilot with the wire brush.  If there is a pop sound when the burner is ignited clean the pilot and the burner openings. You can use the wire brush and canned air. If the flame goes up and down similar to candle light, adjust the pilot by following the instructions on the panel of the furnace.  

Step 3 - Check the Thermocouple

Keep the control knob on pilot; release the thermocouple with a crescent wrench. Use the volt/ohm meter set to lowest voltage. Test the thermocouple for any reading to register. If you don’t get a reading you will need to clean the thermocouple and retest. If you still do not get a reading you will need to replace the thermocouple.

Step 3 – Adjust the Burner

If the flame under the burner is not even, clean the burner openings. If the gas furnace makes a rolling sound while the burners are turned off you will need to clean the burner itself and adjust the air shutter for the burner. When you notice a yellow flame from the burner it is time to clean the burner and adjust the air shutter.

Make sure you take precautions before attempting any repair on a natural gas furnace. You will need to turn the gas on and often during much of these repairs. Make note that the gas valve is in the correct position for the task you are about to perform.