A gas furnace is large rectangular box that intakes cool air and scrubs it with an air filter. It proceeds to heat it up with a gas burner via a steel heat exchanger, and then dispenses the warm air over your homes ductwork through the action of a blower motor. This heated air after cooling down in numerous rooms of the house, returns to the furnace through return air grills. Efficiencies of furnaces are measured in AFUE - Annual Fuel Utilization Efficiency. Things might not always work well all the time, leading to the need for troubleshooting and gas furnace repairs. There are conventional furnaces that need special troubleshooting, and high efficiency condensing furnaces having an efficiency of 90% AFUE, that are a bit complex.
No pilot light or ignition Furnaces pilot lights that dont stay lit may be caused by loose and faulty thermocouples, a clogged pilot orifice or a pilot flame that is set too low. A clogged orifice can be cleared with a thin wire after turning off the gas and shutting circuit breaker controls of the power source off. For gas-fired furnaces, the gas pipe valves should be turned on. For an electronic ignition furnace, the power switch can be turned off then on again to retune the ignition control element. You can then check and clean the flame sensor of the furnace. Checking the owners manual for guides in lighting is also helpful in general for understanding the repairs your furnace may need.
Heating and cycling problems First, you need to make sure the flow of warm air is not blocked and that the thermostat is set properly. The room heating registers should be exposed and the filter should be replaced if dirty. If the furnace does not heat after this, it might be a thermostat failure, a blown fuse, or a tripped circuit breaker. When heat is not produced after adjusting the thermostat, set it to zero. Check for blown fuses and if the circuit breaker is on. The power switch should also be turned on and the motor may have to be reset due to overloads. If the furnace cycles on and off too frequently, the thermostat is likely to be the problem. This can be fixed by making adjustments on it or replacing it - a simple cost in labor vs cost in parts decision.
Furnace blower problems When the motor is running but the blower is not circulating air, the belt that joins them is probably broken. This can be replaced by turning all power to the unit off together with the gas valves, removing the front door, and getting an exact replacement.
When you do not succeed in your gas furnace repairs after troubleshooting, you should contact a professional HVAC contractor since he will most assuredly be able to identify the problem for you and give counsel on the best course of action.
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