How To Fix a Furnace + Infographic [Step by Step Guide 2017]

How To Fix a Furnace


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Gas Furnace Flame Not Visible

If your gas furnace has a pilot light, try adjusting the flame height until it is 1 1/2 to 2 inches tall and contains no yellow color by turning the flame adjustment screw as instructed in your owner’s manual.

Your pilot light’s orifice may be clogged; turn off the power and gas supply, then take a thin wire and push it through the pilot light orifice to remove any debris which may have accumulated.

If your furnace has an electronic ignition, turn down the thermostat and then turn it up five degrees above the current room temperature to reset the switch. Listen for the sound of a spark and/or watch for the glow of the ignitor.

My Furnace Isn’t Producing Enough Heat!

Check your air filter. A dirty or clogged air filter forces your furnace to work inefficiently and can reduce the amount of heat you receive in each room.

Make sure all of your registers are wide open and unobstructed from objects within each room.

Adjust the thermostat five degrees higher than the current room temperature to determine whether your unit is still malfunctioning. If you still aren’t receiving enough heat, call a furnace technician.

My Furnace is Running But I Feel No Warm Air

Turn off the power and gas supply to your furnace, then open up the door which provides access to the furnace unit. Check the belt that connects the furnace motor to the blower; if it is broken or worn, write down the exact number stamped on the belt.

Next, visit your local hardware store and purchase the appropriate replacement belt based on the information you have written down.

Replace the belt by slipping it on the smaller motor pulley first, then rotating the pulley until you can slip the belt over the larger blower pulley. If you need more slack, loosen the motor mount, then re-tighten it once the belt is in place.

If instructed in your manual, oil the bearings in your furnace motor and blower.

My Furnace Blower is Constantly On!

Check the settings on your thermostat. If the “Fan” setting is “On”, switch it over to “Off” or “Auto”. If this is not the issue, you’ll need to check the limit switch.

The limit switch is designed to shut off the furnace when the plenum reaches a certain temperature. With the help of your owner’s manual, adjust the lower pointer of the switch to around 90 degrees F and the upper pointer to around 115 F.

My Furnace Keeps Making Noises

Tighten any screws contained within the furnace cabinet to reduce rattling sounds from the area.

If you hear squealing, turn off the power and gas supply, then check the belt between the motor and blower. With the help of your manual, adjust, realign, or replace the belt if you discover a problem.

Grinding noises are a sign that your furnace motor has worn bearings and should be replaced. Contact a furnace technician for assistance.

My Oil Burning Furnace is Malfunctioning

Make sure your unit has power by checking any appropriate electrical cords/outlets and verifying that the circuit breaker has not been tripped.

Check the air filter and clean or replace it if it is dirty or in otherwise poor condition.

Replace the thermostat if your furnace is relatively new and/or has suddenly stopped working with no apparent or logical reason, particularly if you suspect it is the cause of the problem.

Verify that the flame sensor is not signaling your unit to turn off with the aid of your owner’s manual.

You may need to contact a furnace technician, as oil burning units are challenging to repair.

JC Heating & Cooling provides their services in:

  • La Grange, IL
  • Western Springs, IL
  • Burr Ridge, IL
  • Hinsdale, IL
  • Glen Ellyn, IL
  • Wheaton, IL
  • Elmhurst, IL