How to Clean a Gas Furnace

How to clean a gas furnace

Preventative gas furnace cleaning and maintenance will ensure your system provides years of reliable service. To keep your furnace in peak condition and avoid emergency repairs, invest a few hours in gas furnace cleaning. With the heating season drawing to a close with the arrival of the warm spring weather, now is the perfect time!

How to Clean a Gas Furnace

No matter what energy source your heating system uses, it needs annual attention. This is especially critical for combustion systems. Luckily, it’s not hard to keep your system in top condition…

  • Gather Essentials
    Ratchet & socket set
    Shop vac or vacuum with upholstery brush attachment
    Small, stiff bristled brush
    New furnace filter
    Emery cloth
    Lightweight machine oil
  • Steps
    1. Turn off power/gas to the furnace.
      Turn off power to the furnace at the breaker box. Switch the furnace’s electrical power switch to the ‘off’ position. Shut off the gas by giving the valve ¼ turn.
    2. Clean furnace surfaces.
      Wipe exterior surfaces with a damp rag. Remove the furnace access door by lifting it up and out. Loosen screws, removing the burner cover (if you have one). Vacuum the burners and furnace base using a shop vac or household vacuum with wand/upholstery attachment. Use extensions if necessary, doing your best to reach the back. Don’t forget to lift the blower door and vacuum the compartment. Look for signs of soot, which indicates poor combustion and a need for attention.
    3. Remove the blower.
      Unscrew the control panel if it blocks the blower, letting it hang. Use a socket and ratchet, removing the bolts that hold the blower. Gently remove.
    4. Carefully clean the blower.
      Without disturbing the wiring and counterweights on fan blades, carefully clean the blower with a vacuum and small brush. Not cleaning it thoroughly could throw-off balance.
    5. Clean the pilot or hot surface igniter.
      Using a drinking straw, carefully blow dust off the pilot with your breath. A dirty pilot could give a false reading. New furnaces? You may have a hot surface igniter. If so, leave it in place, blowing the dust off using a straw. Do NOT touch this part – it breaks very easily! (Replace the furnace doors gently, later, to safeguard it.)
    6. Clean the flame sensor.
      Pull the flame sensor down and out of its bracket, lightly cleaning it with a fine emery cloth. Slide it back in. If the sensor is dirty, it can prevent your furnace from lighting.
    7. Inspect the drive belt.
      Check the blower belt for cracks/fraying. Replacement costs less than $10. Tension the new belt to deflect ½-3/4-inch.
    8. Lubricate (but not too much).
      Remove and clean oil caps. Oil the two blower motor and shaft bearings. Apply only 2-3 drops of lubricating oil – don’t overdo it!
    9. Replace the air filter.
      Change the furnace filter. It should be changed every 3-months, at a minimum, to protect the system. Don’t upgrade to a higher-efficiency filter without checking manufacturer recommendations. Doing so can strain the blower motor and sabotage efficiency.
    10. Activate the burners.
      Turn the power and gas back on, activating the burners by turning up the thermostat. Check that burner flames are even and blue. Yellow flames indicate dirty burners. Cleaning and adjusting burners is NOT a DIY job. Call a pro.
    11. Adjust dampers.
      If your heating ducts also serve as AC ducts, adjust the dampers for seasonal settings.

Looking for a faster, easier way to accomplish seasonal furnace maintenance? Skip all 12 steps above, and contact Aire Serv® to schedule gas furnace maintenance today.

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