The Complete Maintenance Guide: How to Keep Your Furnace Running At Its Best

The Complete Maintenance Guide: How to Keep Your Furnace Running At Its Best

The Complete Maintenance Guide: How to Keep Your Furnace Running at its Best

The secret to enjoying the cold winter is having a warm and cozy home. Sometimes, maintenance of the heating system is overlooked until the unit stops working properly. By then, the system could need a major repair. Having your furnace well-maintained will prevent sudden malfunctions, and you will save a lot of money in the long run.

Important Note: Before you do any work on your furnace, make sure to shut the power OFF so you can work safely.

The power switch to the furnace is often located next to the furnace – either on its side or on a wall nearby. You can also turn off the power in the breaker box.

Maintenance is Important: Check the Owner’s Manual

The owner’s manual that came with your furnace tells you exactly what should be done to the unit and when it should be done. If you’ve lost the manual, check for it online. Most furnaces work in similar fashion, but you can also specify the make and model to get the precise instructions.

Essential Parts and Their Functions

The furnace has two main compartments: the bottom, where cool air is drawn in; and the top, where the air is heated.

The filter and the blower wheel are located in the bottom. The blower sucks in cool air and pumps it to the top compartment, where it is warmed. There’s also a control board in front of the blower chamber.

The top part of the furnace has some important pieces including, from top to bottom:

  • Draft Inducer Motor: As the name implies, the draft inducer motor provides draft for safe and clean combustion. It sucks flames through the heat exchanger (a chamber in the back where the air is heated up). Then, the motor blows the combustion gases through an exhaust pipe.
  • Heat Exchanger: The heat exchanger is a chamber that separates the combustion gases from the house air. Inside that chamber, which is not visible, there are tubes in a zig-zag shape, that heat the air (they get very hot).
  • Burners: The burners are the cylinders on the bottom front. They produce flames with the help of igniters attached to the burner cover.
  • Flame Sensors: Flame sensors, also called the flame rod, are connected to the other side of the burner cover. They sense whether flames are being produced. If the igniters aren’t working, there won’t be any spark and only gas will come through the burners. The flame sensor will then shut off the furnace.

To distinguish which is which, the flame sensor has one white cable connected to it, while the igniters have two.

After identifying these essential parts, you can start the maintenance with a better understanding of how the furnace works and where it should be cleaned.

Tips for Maintaining Your Furnace

Change Filter Frequently:

The filter is crucial to keeping your furnace clear of debris that could impact the airflow and affect the efficiency of the unit. The filter should be replaced every month or so. The one-inch filter should be replaced every three months. Even if it still looks white, it’s not necessarily clean.

If you’re renovating your house, change the filter frequently because drywall dust and other particles will be sucked in and get stuck on the filter.

Also, if you get your ducts cleaned, some of the dust and debris that was in the ducts could lodge in the furnace filters.

Keep in mind that the filters are directional and the arrows on the package should be pointing to the furnace.


For the humidifier, set the damper to the winter setting. It’s also a good idea to replace the inner water panel. By adjusting the humidifier to around 35% to 40%, the air feels warmer, so, you won’t need to set the thermostat as high. Your house will be warm and a lower temperature setting on your thermostat will reduce the amount of work your unit has to do.


Some thermostats run by batteries, usually AA. When the batteries are dying, the thermostat screen often shows a weak battery icon. Replacing worn batteries will help keep your thermostat working properly.

Keep Return and Supply Registers Open:

You should keep the vents open and clean. You can vacuum the outside and inside of the register. This is important to airflow and to avoid the furnace operating unnecessarily.

You can close some of the vents, but it is recommended that you do not close more than one-third of the vents.

Also, you may have to make adjustments on the dampers on the ducts during the winter. Some homes with two storeys have two supply ducts.

Keep Parts Clean:

Cleaning the inner parts is one of the most important things you can do to maintain your furnace. To do that, remove the unit’s doors (be mindful of how you took it off so you can put it back on the same way).

  • Vacuum Inside: Vacuum the accumulated dust and debris from the burners and the furnace base. Tape a thin drain line into the vacuum hose to clean small corners and at the back of the burners.

For the blower wheel, unscrew the bolts that hold the control board (you can leave it hanging). Unscrew the blower and gently pull it out of the furnace. With a thick-bristle brush, carefully dust the fins. You must be gentle. Besides the blades being sharp, you don’t want to move the wires too much or unbalance the blower.

  • Clean Flame Sensor: To locate the flame sensor, look at the pipes outside of the furnace. Follow the pipe that has a gas valve (normally yellow or red) into the furnace. The gas control valve will have the flame sensor attached to it. Unscrew the bolt and take out the sensor.

Over time, the rod will accumulate carbon that should be cleaned off. Use a scouring pad to scrub the rod.

  • Furnaces with PVC Pipes: For high-efficiency furnaces, it’s important to clean the PVC pipes. Inside the furnace box, the pipe leads to a chamber that will be attached with six to eight bolts. Unscrew the door. Clean any leaves, dead bugs, and other debris with a brush or vacuum cleaner.

Check the Drive Belt

If your furnace is belt-driven, search for any worn-out part or cracks. To check the pressure of the belt, press it in the middle with your finger. It should deflect ½ to ¾ of an inch. To replace it, untighten the motor bolt, take the old belt out, put the new in and tighten the bolt back in. Adjust to the recommended tension.

Checking and Cleaning Ducts

You may want to call in a professional for this, but if you prefer to take this on as a do-it-yourself project, here are some tips.

  • Cover supply registers with a paper towel
  • Set the thermostat to fan mode
  • Ensure that the furnace filter is in place
  • Tap around the ductwork to loosen any deposits of dust
  • Go back to the supply registers, use a brush to clean the grills, and clean the area around it, vacuum inside as deep as your vacuum cleaner hose will reach
  • Remove the paper towel covering the registers
  • Repeat the previous step with the return air registers, making sure to clean grills, and vacuum everything inside and outside
  • Turn off the fan and the power going to the furnace and clean inside of it.
  • Replace furnace filters

Have Regular Professional Maintenance

The best way to extend the life of your furnace is to have regular professional maintenance. A certified technician will know exactly what do to. They will check inside of burners, fix wires, inspect fans, and much more. Regular maintenance will save money by preventing major repairs in the future and you will get the most out of your furnace.

If cleaning and checking the furnace seems daunting as a DYI project, call the experts at Forney Air at (214) 924-9745 for fast service at competitive prices.


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