subject: Repairing a Gas Furnace [print this page] A furnace is an enclosed structure designed to produce heat. It is extremely important in places that get harsh winters. Fuel sources such as natural gas, fuel oil, coal or wood are needed depending on the type and purpose of the furnace. Household furnaces are of two types - combustion or condensation. Combustion furnaces burn fuel and hence need exhausts. Both of these types need regular maintenance and furnace repair according to the safety directions provided by the manufacturer in case something goes wrong.
Gas furnaces are easier to operate and present fewer problems than most other kinds of furnaces. The pilot light controls, gas valves, reset buttons and the thermocouple, are all located in the front of the furnace. The thermocouple is a measuring device that checks the potential and acts as a safety device for switching the machine off if there is a problem. If the pilot light still does not remain steady or keeps going on and off then an attempt to set it right by simply tightening the thermocouple nut slightly without using too much pressure can be made. But if the problem persists, then the thermocouple has to be replaced.
This can be done in a few simple steps. A wrench and a replacement thermocouple are all that you will need. A replacement thermocouple can be purchased from a furnace repair shop. First, remove the copper lead and connection nut inside the connection to the gas line. Unscrew the nut that holds the thermocouple tube in place. Insert the new thermocouple into the space in the bracket with the steel tube up and the copper lead down. Make sure that it is clean and dry. The bracket nut should be tightened just right, not using too much pressure. A simple rule that you can keep in mind is that the nut should not be much tighter than if it had been tightened just with your hands.
Another potential problem is the limit switch, which shuts off the burner if the plenum or main chamber gets overheated. If the temperature drops too much, it switches off the blower. If the blower continues to work then check whether the thermostat is in the ON position and change to auto if it is. If it is already on auto, then the limit switch needs to be adjusted. Once the control cover is off, a dial marked limit on one side and fan will be displayed. On the fan side, two pointers which start/stop the blower at the higher/lower settings are found. Set these 25 degrees apart. Do not touch the limit side of the dial.
While dealing with any furnace repair, make sure that there is no smell of gas. If there is, you should investigate the leak. Once a leak has been identified, do not turn on any switches or attempt to turn the gas off, lest a spark so created may ignite the gas vapor. Just call a professional furnace maintenance company and go out of the house until they arrive.
