DIY Guide: How To Service Your Furnace

By HomeAdvisor

Updated October 19, 2016

HVAC system

On This Page:

  1. DIY Furnace Maintenance
  2. What a Pro Will Do
  3. Conclusion

Once a year, your furnace needs inspecting and servicing. Skipping this can cause it to fail and leave you cold, or it can cause deadly carbon monoxide to fill your home. The good news is that you can do a lot of the maintenance yourself.

  • Difficulty – Hard
  • Time needed – About 3 hours
  • Cost – About $30.00 to $50.00
  • Tools needed
    • Screwdriver
    • Wire brush
    • Shop vacuum
    • Strap wrench
  • Materials needed
    • Foil tape
    • Air filter
    • Oil filter (for oil systems)
    • Oil nozzle (for oil systems)

DIY Furnace Maintenance

Before Doing Anything Else

If your furnace has stopped working, here are a few things to check before opening up the unit:

  • If your unit has a separate power switch, check that it’s in the “on” position. This may seem incredibly simple, but it’s often overlooked.
  • Check for tripped circuit breakers and/or blown fuses. If the fuse blows or the circuit breaker trips when the unit turns on, shut it down and call a professional.
  • If there is a reset button, wait half an hour to make sure the motor cools down before pressing it. Repeat this three times if necessary. (The RESET button should be clearly marked and near the motor housing.)
  • Check the thermostat setting. Step it up 5 degrees to see if the unit turns on.
  • Check the fuel supply. If you have a gas furnace, be sure the gas valve is open and the pilot light is lit. If you have an oil furnace, check the oil level.

Before Starting Work

Before opening the unit, read the following:

  • Make sure all power to the unit is off. Trip the circuit breaker or remove the fuse. If you can’t identify which one it is, throw the mains. Remove the main fuse or trip the main circuit breaker to the whole house. It should be clearly marked. If your unit has a separate box, you can shut it off there.
  • If you have a gas furnace and smell gas, get out of the house. Don’t turn any lights off or on. Leave the doors open. From the safety of the sidewalk, call the fire department or gas company to report the leak. Don’t call from inside your house as any spark or electrical signal could cause an explosion.

Blower and Motor

To clean the blower you will need: a screwdriver, a replacement filter, a toothbrush, a vacuum cleaner, and clean rags.

Inspect and clean or replace the filter. This should be done at the start of the heating season and then once per month while using the unit. Filter: $2.00 to $15.00 depending on quality.

Clean the blower assembly including bets, pulleys, and housing. The blower will be located behind the filter.

Clean the blower fan. Remove the blower. It should be held in place by screws. If the power cord is too short, disconnect it, marking which wire goes where so you can put it back together right. Use a toothbrush to clean the blades and spaces between the blades. Then use a vacuum to clean out the debris you’ve knocked loose.

If your motor has oil ports, put 2-3 drops of 10-weight non-detergent motor oil to each port. Do not use all-purpose oil, and do not over lubricate. Repeat for the blower shaft if it has ports. This should be done once a year. Oil: $2.00 to $3.00 a quart.

Inspect the belt

The motor belt should be firm, giving no more than ½ inch when pressed. It should also be free of cracks and damage. To remove the belt, you will need a wrench and a replacement belt. Loosen, do not remove, the motor bolts. You only need them loose enough to move the motor and slacken the belt. Remove the belt and inspect it, replacing it with a new one if necessary. Belt: $4.00 to $6.00.

Check vents and chimneys

Go outside and make sure any vents and chimneys are not blocked by snow, debris, nests, etc.

Check ducting for leaks

Look for separation at the duct joints and seal with metal tape. After you’ve serviced and turned it back on, feel for leaks that might not be so obvious and do the same.

Oil furnaces

There are a couple of extra steps for an oil furnace:

  • Replace the oil filter. You will need an oil filter wrench and something to catch the oil in. When replacing the filter, run some oil around the gasket to make sure it fits smoothly. Oil filter insert: $4.00 to $5.00. Wrench: $6.00 to $10.00.
  • Bleed the lines according to your unit’s manufacturer instructions.
  • Clean around any oil fittings and inspect for leaks. Tighten if necessary.

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What a Pro Will Do

While there is no industry standard, most HVAC professionals will do the following as part of their furnace servicing:

Gas Furnace

  • Check vents.
  • Analyze combustion gases.
  • Check blower door.
  • Check for blockage at intake points.
  • Inspect heat exchanger.
  • Inspect burners.
  • Check drainage system including internal hoses.
  • Check drain and trap.
  • Remove and inspect blower wheel.
  • Test the amp-draw on motor.
  • Inspect belts.
  • Inspect wiring.
  • Check filters.

Oil Furnace

  • Check overall condition.
  • Clean heat exchanger.
  • Remove/clean flue pipe and chimney base.
  • Inspect clean-out doors.
  • Inspect oil burner.
  • Inspect and replace oil nozzle.
  • Inspect end cone.
  • Inspect electrodes and belts.
  • Replace oil filter.
  • Replace fuel pump strainer if applicable.
  • Inspect flame sensor.
  • Inspect electrical system.
  • Oil motor if applicable.
  • Clean burner fan.
  • Check pump pressure.
  • Check vacuum readings.
  • Perform safety check.
  • Check combustion efficiency.
  • Ensure the fire is clean.
  • Check carbon dioxide.
  • Check fuel level.

This service costs $100.00 to $150.00 a year. This cost can prevent thousands of dollars in repairs.

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In Conclusion

If you have any doubts as to your ability to do the project, call a professional. Regular maintenance is the best way to keep your furnace running well, and an ounce of prevention is worth a pound of cure.

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