| To fix household things that break, you need to | | | | your local hardware store. Others, such as burners |
| know how it works, what can go wrong, how to | | | | and controls, must be purchased from the |
| identify the problem, as well as the steps to fixing it. | | | | manufacturer or aftermarket supplier or through a |
| Here's what you need to know about gas furnace | | | | heating equipment supplier listed in your local |
| repairs. | | | | telephone book. |
| How Does It Work? | | | | The primary tools you will need for fixing a gas |
| Natural or propane gas from an outside source is | | | | furnace include these: |
| piped to the furnace where it is burned to produce | | | | * Screwdrivers |
| heat. Usually a fan-driven forced-air distribution | | | | * Wrenches |
| system blows the warmed air through ducts that | | | | * Pliers |
| vent into the various rooms of the house. Older gas | | | | * Wire brush |
| furnaces use a standing-pilot ignition. Maintenance | | | | * Multimeter |
| involves turning off the pilot each spring and relighting | | | | What Are the Steps to Fixing It? |
| it each fall. Newer, more efficient gas furnaces use | | | | To light the pilot on a standing-pilot (always on) |
| an electric spark to light the gas as necessary. | | | | ignition system, follow the lighting instructions located |
| What Can Go Wrong? | | | | near the control. Otherwise, try these steps: |
| Most gas furnaces are quite reliable. What are the | | | | Light the pilot: |
| symptoms of problems? The furnace may not | | | | 1. Press and hold the pilot control knob to start the |
| produce heat or may not produce enough heat. The | | | | pilot. Set the control knob to the pilot position. Hold a |
| pilot light may go out repeatedly or refuse to light. | | | | long match under the pilot gas port. |
| The thermocouple may be faulty. The pilot may light | | | | 2. Press the control knob; the pilot should light. Hold |
| but not ignite the burner. The furnace may be noisy. | | | | the control knob down until the flame is burning |
| There are some maintenance and a few minor | | | | brightly (about 30 seconds). Release pressure on the |
| repairs that you can make. However, major service | | | | knob, and turn it to the on position. |
| should be left to a trained technician. | | | | 3. If the pilot goes out when you release the control |
| Fix-It Tip | | | | knob, try relighting, holding the control knob down |
| To minimize problems with your gas furnace, take | | | | longer. If the pilot again goes out, check the |
| time each month to check the air filter and clean or | | | | thermocouple (below). |
| replace it if necessary. Once a year, clean the blower | | | | Adjust the pilot: |
| blades, lubricate the blower motor, and inspect the | | | | 1. Remove any cap covering the pilot adjusting screw |
| belt. | | | | on a combination control. |
| How Can I Identify the Problem? | | | | 2. Turn the adjusting screw counterclockwise to |
| If there is no heat, check the electrical service panel | | | | increase the flame or clockwise to decrease it. It is |
| for a burned fuse or tripped breaker. Relight the pilot | | | | correctly adjusted when the flame envelops the |
| light (see below). | | | | thermocouple bulb by 1/2 inch and appears dark blue |
| If there is not enough heat, adjust the burner air | | | | with a small yellow tip. |
| shutter (see below); and clean the burner ports (see | | | | Test and replace a thermocouple: |
| below). | | | | 1. Hold the control knob to pilot and light the pilot as |
| If the pilot light does not light or does not stay lit, | | | | above. |
| clean the pilot orifice carefully with a toothpick, test | | | | 2. Unscrew the thermocouple fitting with an |
| the thermocouple and replace it if it is faulty (see | | | | open-ended wrench. |
| below). | | | | 3. Set a multimeter to the DVC (lowest voltage) |
| If the flame flickers, adjust the pilot (see below). | | | | scale. |
| If there is an exploding sound when the burner | | | | 4. Clip one multimeter lead to the end of the |
| ignites, adjust the pilot to a higher setting and clean | | | | thermocouple tube nearest the pilot and the other |
| the pilot orifice and the burner ports. | | | | lead to the fitting on the other end of the tube. |
| If the burner takes more than a few seconds to | | | | 5. If the multimeter shows a reading besides zero, |
| ignite, clean the pilot orifice and adjust the pilot light. | | | | the thermocouple is functioning. Replace the |
| If the burner flame is uneven, clean the burner ports. | | | | thermocouple tube. |
| If the burner flame is very yellow, clean the burner; | | | | 6. If there is no reading, you will need to clean or |
| open vents in the furnace room to provide more air; | | | | replace the thermocouple following steps 7 through |
| adjust the burner air shutter. | | | | 11. |
| If the furnace makes a rumbling noise when the | | | | 7. Release the control knob and shut off the main |
| burners are off, clean the burner and adjust the | | | | gas valve on the gas-supply pipe that leads into the |
| burner air shutter. | | | | burner. Shut off power to the burner at the electrical |
| If the air is too dry, wash or replace the evaporator | | | | service panel . |
| pad if you have a humidifier; test the humidistat; and | | | | 8. Remove the thermocouple from its mounting |
| adjust the water-level float to raise the water level. | | | | bracket. |
| If some rooms are too cool and others too warm, | | | | 9. Wipe the combination control clean and install a |
| the distribution system may require balancing. Refer | | | | new thermocouple, tightening it by hand, then give it |
| to the Forced-Air Distribution Fix-It Guide at Fix-It Tip | | | | a one-quarter turn with a wrench. |
| Be sure your filter is the right size for your furnace. | | | | 10. Insert the thermocouple into the pilot bracket, |
| What Parts, Materials, and Tools Do I Need? | | | | being careful to not crimp the tubing. |
| Some replacement parts for gas furnaces are | | | | 11. Turn on power to the furnace and relight the pilot |
| interchangeable (filters, fasteners) and available at | | | | (above). |