Furnace Not Working? The 5 Most Common Causes

Today you’re going to learn exactly how to find out why your furnace isn’t turning on.

Let’s get started.

• • Step #1: Check your Air Filter
  • Step #2: Check Your Pilot Light
  • Step #3: Check Your Thermostat
  • Step #4: Check The Power
  • Step #5: Check Your Gas Supply

  When your furnace doesn’t come on, it can be very aggravating because it’s cold in your house. It’s even more frustrating when you can hear the heater clicking on and getting ready to blow the toasty hot air…but then nothing happens.

  Most newer model furnaces are designed for reliability (assuming they’ve been maintained) over a long period and are one of the most expensive and most needed appliances in almost every home.

  Reasons for your gas furnace not working can be complicated or very simple. While you are probably better off leaving the difficult problems of thermocouples, wiring, heat exchanger, and blower motors to a qualified professional, there are a good number of things you can check before you phone a qualified HVAC contractor for furnace repair service.

  Before you attempt to fix a furnace that won’t start, make sure you know what kind of furnace you have. The most common in this area is forced air and gas (propane, fuel oil, and natural gas) furnaces.

  Here are 5 easy things you can do on your own to troubleshoot why your furnace isn’t working:

  Check to make sure the furnace filter is clean.

  If the air flow out of your registers seems low, check the air filter. A clogged filter can block air flow. Make sure all your air registers are open and not obstructed with dust or objects.

  Check the pilot ignition light.

  (Electronic ignitions will not have a pilot light.) If your furnace clicks on or initiates the start cycle, but does not fire up, you likely have a faulty or dirty ignitor/sensor. This is one of the most common furnace problems. Under normal conditions, the furnace is notified by the thermostat to click on, the ignitor gets red hot and then initiates the entire process of igniting the gas and blowing the warm air.

• If You Feel Comfortable: Check the error codes in your furnace user manual to make sure you do not have a more severe problem. To fix the furnace that won’t start, turn off the power to the furnace and turn off the gas. Remove the front panel and look for the ignitor/sensor. Refer to your manufacturer’s user manual to locate the ignitor. It is usually found near where the flames shoot out of the burners. Basically, the furnace will not continue in the starting sequence because the sensor/ignitor is dirty and needs to be cleaned.

• Bonus Tip: Clean Sensor

• Removing the sensor with a screwdriver is easy. Clean the probe on the sensor by rubbing it with some medium grain sandpaper. Do a precise job, but be careful not to break anything. Replace the sensor exactly the way you found it. Put the front panel back on, turn on the gas, and then turn on the power. Turn up the temperature on your thermostat to see if your furnace will fire up. If this doesn’t solve the problem, time to give a technician a call.
  

  Check your thermostat.

  Make sure the temperature control selector is set above the current room temperature, and the system switch is on the AUTO or HEAT position. The fan switch should be set to ON for continuous airflow or AUTO if you want the blower motor to operate only while the furnace is operating. Try to get the furnace to turn on by raising the thermostat to its highest temperature setting.

  Check to make sure power to the furnace is on.

  There’s a power disconnect switch by the furnace, even gas systems use electricity. Check the fuse/circuit breaker at the electrical panel for the furnace to make sure the breaker has not tripped. Make sure the power switch next to the furnace is in the “On” “position.

  Finally, make sure the propane gas supply (or other fuel) to the furnace is open.

  Check to make sure the gas valve to the furnace is open. A disruption of the gas supply to your heating system could leave your heating system without fuel. If you smell propane leak, leave your home immediately and then call your propane supplier and a local HVAC contractor for emergency repair.