How to Repair a Gas Furnace

If you are wondering how to repair a gas furnace, then here is an article that presents you with all the basic instructions on repairing a malfunctioning gas furnace. Repairing a gas furnace is, no doubt, a bit tedious. But with a sound understanding of how a gas furnace works, its different parts and their function, and the problems that tend to occur in different parts, troubleshooting gas furnace problems is easy.

How Does a Gas Furnace Work

Natural gas or propane is the fuel for a gas furnace. The fuel is taken in from an outside source and burned to form heat. There are fans to blow the warmed air through the ducts to distribute heat throughout the room. In older gas furnaces, there used to be a standing-pilot ignition. The pilot had to be put out in the spring and lit in the winter. In newer furnaces, an electric spark is used to ignite the gas.

Problems With a Gas Furnace

Your gas furnace is working well if the flame is full, continuous, and doesn't sputter. A gas furnace becomes problematic when it does not produce heat or does not produce a sufficient amount of heat. A problem can occur in any of the gas furnace parts i.e. the pilot, the blower, or the burner. Any malfunctioning part can impair the normal functioning of the gas furnace as a whole. Some of the frequently occurring problems are - a defect in the thermocouple; the pilot light repeatedly goes out or doesn't light at all; the pilot itself gets lit but fails to ignite the burner; the furnace sputters; the gas furnace is leaking. The last is the most common problem. Of course, the smell of the gas is enough to suggest that there is a leakage problem in the gas furnace. Still, at any point, if you feel you need to confirm the leakage, then conduct the test given below.

Test to Confirm a Gas Leak

If you suspect leakage of gas from the gas furnace, there is a way to confirm it. Prepare a solution of water (1 cup) and detergent (1 tsp). Paint it on the gas supply pipeline, on the valves and connections. The soapy water bubbles at the point of leakage. If you find a leak, tighten the leaky connection with a pipe wrench, or seal the leaky area with a sealant. If the problem prevails, call a professional.

Repairing a Gas Furnace

If the problem with your gas furnace is major, you must consult a technician. In case you feel there is a small defect and you can rectify it, then you should always encourage yourself as nothing is better than taking care of your possessions yourself. To troubleshoot gas furnace problems, learn to identify the problem in the first place.

Problem Identification

• If you find no heat, check for the supply of electricity. You might find a burned fuse or a damaged breaker.
• If the heat produced is not enough, a dirt-blocked burner port is the most obvious reason. Clean it, and also adjust the shutter of the air burner.
• In case there is a problem with lighting the pilot, or once lit it doesn't stay that way too long, then the pilot orifice is not clean enough. You can clean it with a toothpick. If the flame is not steady, adjust the pilot.
• If the thermocouple is faulty, the ideal option is to replace it.
• If the burner sputters on ignition or takes more time to ignite, there is a blockage of the pilot orifice by dirt and dust. Set the pilot at a higher level and clean the orifice along with the burner ports.
• If the burner flame is very yellow, the burner needs to be cleaned. If the burner flame is uneven, the burner port needs to be cleaned.
• If you find the air too dry, the evaporator pad needs to be washed or replaced (if you have a humidifier). Test the humidistat. Adjust the float in order to raise the water level.
• If there is uneven distribution of heat, i.e. some rooms are too cool and the rest too warm, there is a problem with the distribution system.

Troubleshooting Gas Furnace Problems

Some gas furnace parts like filters and fasteners are interchangeable. They are available in hardware shops. Other parts such as burners and controls can be bought from an aftermarket supplier, manufacturer, or a heating equipment supplier. You'll need pliers, wrenches, multimeter, a wire brush, and a screwdriver to repair a gas furnace.

1. Start the pilot by pressing and holding its control knob, and set it to the pilot position. Ignite the burner with a long match. Hold the control knob down till the flame burns brightly. Release pressure from the knob and set it to the 'on' state. If you find the pilot going out when the control knob is released, hold the control knob a little longer. If it happens again, check the thermocouple.
2. Light the pilot as described above. Use an open-ended wrench to unscrew the thermocouple fitting. Set a multimeter to the lowest voltage scale.
3. Clip one multimeter lead to the end of the thermocouple tube that is closest to the pilot and the other lead to the fitting on the other end of the tube.
4. If the multimeter shows a non-zero reading, the thermocouple is working; only the tube is faulty and needs to be replaced. Otherwise, you need to replace the thermocouple.

Steps to Replace the Thermocouple:

• Put off the electricity supply by releasing the control knob and turning-off the main gas.
• Take out the thermocouple from its mounting bracket.
• Clean the combination control. Install the new thermocouple. Tighten it and give it a one-quarter turn with the help of a wrench.
• Place the thermocouple inside the pilot bracket. Be sure not to bend the tubing.
• Put on the electric power to the furnace and rekindle the pilot.

By now, you must know to repair a gas furnace, and you must be feeling confident to repair your troublesome gas furnace and save a few dollars that you would otherwise spend on a technician.