Furnace Troubleshooting, Before You Call The Repairman...With our furnace troubleshooting guide, you can do it yourself and save a lot of money. The average service call will cost you over $100. We help you keep that money! Just look at a sample of what our visitors tell us: I was so happy to happen on to your site! I was having problems heating my home, and the weather has been about 0 for the last few days and my electric furnace just wasn't keeping up. I had a problem with a heat sequencer and although I suspected it was the problem, I was able to make a definite determination that it was indeed my problem after using your troubleshooter! I replaced both sequencers and voila, $55 dollars later (for two new sequencers), and my house is warming up very quickly. I just repaired it about 45 mins ago and already I have had an 7 degree rise and counting!!! Thanks again! -Frank from Park Hills, Mo. U.S.A. Thank you! Thank you! Thank you! I woke up this morning to a 59 degree house. The outside temperature was hovering around zero. By following your troubleshooting guide I was able to repair my furnace before the service technician arrived. Ernest from Rossford, Oh. U.S.A. **NOTE** ONLY YOU CAN ASSESS YOUR ABILITY TO PERFORM THIS TASK. THIS IS A GUIDE AND CANNOT PROVIDE ALL OF THE DETAILS FOR EVERY SITUATION. Proper maintenance will help you avoid many common furnace problems. Before you start troubleshooting, make sure you have performed the suggested maintenance. This guide will cover furnaces that burn natural gas or propane. You can use our electric furnace troubleshooting guide for an electric unit or heat pump. You can use our oil furnace repair guide for units that burn fuel oil or waste oil.
Begin your diagnosis at the thermostat. Ensure that the thermostat is on heat and the setpoint is above room temperature. If the furnace fan is not running, place the fan in the on mode. Now, go to the furnace to continue your diagnosis. If the fan is not running, check the breaker, fuse, and/or the switch for the furnace. If the breaker was tripped, leave it off and check the furnace wiring for loose connections. Also, you should look for burn spots on the control board and replace the board if spots are found. After any necessary repairs, the breaker can be reset.
If the breaker or fuse was not tripped, the problem could be the transformer, thermostat, furnace control board, the blower motor, or its' run capacitor. If you have a condensate pump, ensure that its' reservoir is not full. On most units there is a float switch that will stop the furnace from running if the pumps' reservoir is full. If the reservoir is full, then check the power to the unit and replace the pump as required. After the blower motor is running, the fan can be placed back in the automatic mode at the thermostat.
If the furnace uses a standing pilot, ensure that it is lit and the flame is touching the tip of the thermocouple. If it is not, you can go to thermocouple replacement for further troubleshooting. If the pilot is lit but the main burners do not come on, you should feel the side of the furnace. If the side of the furnace is not warm, the problem could be the thermostat, furnace control board, limit control or the gas valve. If the side of the furnace is warm, allow the unit to cool, then continue your furnace troubleshooting. If the furnace has an inducer motor, check to see that it is running. If it is not, the inducer assembly or the control board could be the problem. If the inducer motor is running, does the pilot try to ignite? If it does not, the flue could be blocked, the furnace control board could be bad, or the limit control could be the problem. If the pilot tries to light but goes out, the
pilot assembly
or flame sensor could be dirty.
If the furnace doesn't use a pilot, does the ignitor come on? If not, the ignitor may need replacement or the furnace control board could be bad. Once the pilot or ignitor is on, do the main burners light? If not ensure that you have gas supplied to the furnace. If you have gas, the problem could be the gas valve or furnace control board. If the burners come on but do not stay on for more than about 3 seconds, the flame sensor could be dirty or the furnace control could be bad. On condensing furnaces, if the burners come on for longer than 5 seconds but turn off before the thermostat is satisfied, the condensate drain could be plugged. Most of these units have a built in trap and sediment can build up in it. This can cause the furnace to operate abnormally. Once the burners stay lit, the blower motor should start after a delay of from one to three minutes. If the blower does not start, the problem could be its' run capacitor or the motor. You should complete your furnace troubleshooting by observing the units' operation through a complete heating cycle. At the end of the cycle, the fan should run for about 2-3 minutes after the burner shuts off. If the fan does not shut off after the time delay, then the fan/limit control (on older units) may be sticking and require replacement.
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