Why Is a Residential Furnace Not Working?

March 19, 2019

A high-quality residential furnace should last for many years if not even a decade or two before it needs significant repairs or replacing. However, this doesn’t mean you’re guaranteed to own a furnace without any problems or breakdowns during that time! Any number of issues, including outright neglect of needed maintenance, can lead to a furnace that doesn’t engage, blows cool air, or that cycles off too quickly.

Common causes for a residential furnace to fail:

  • Thermostat malfunction
  • Clogged filter
  • Furnace safety switch is engaged
  • Malfunctioning burner
  • Improperly sized furnace
  • Dirty ductwork in the home
  • Furnace blower malfunction
  • Furnace has exceeded its lifespan

While only a furnace repair contractor near your area can pinpoint the exact reason your home’s furnace is malfunctioning, you might note a few common causes of needed furnace repairs. You can then try some simple furnace troubleshooting fixes on your own and note if this gets your home’s furnace working again!

furnace hookup in residential house

Furnace Not Igniting

Before you assume you need a new residential furnace, start with some simple and obvious reasons for a furnace to break down:

  • If your home’s thermostat runs on batteries, change the batteries and note if the furnace then cycles on and off as it should.
  • An electrician can check the wiring of the thermostat to ensure it’s not corroded or damaged or if it needs updating.
  • Note if there is a heat source near the thermostat that might cause it to read the room’s temperature inaccurately.
  • Check the home’s circuits or fuses. A visual inspection is insufficient; flip circuit breakers off and then on again, or replace the fuse for a proper check of their function.
  • For gas furnaces, note if the pilot light is working and the color of the flame. A yellow flame is dirty and may not heat air properly. Turn off the gas source to the furnace and clean the valve with a pipe cleaner and then relight the furnace.
  • If the flame is blue, note if there is a breeze around the furnace that could be interfering with the strength of the flame and address that airflow as needed.
  • A furnace will have a safety switch near its power button; this switch turns off the furnace if it should overheat. Note if the safety switch is off and turn the furnace back on if needed.

Troubleshooting the Blower

If your home’s furnace switches on but you notice that airflow through the home is very weak, or that certain rooms don’t get warm at all, this often signals a problem with the furnace blower. The pulley between the two parts of the blower motor may have snapped or weakened over time; a homeowner can often replace this part on their own. Be sure you use the pulley make and model meant for your home’s furnace in particular!

If the furnace produces lukewarm air or airflow is limited, this might indicate a problem with what is called a limit switch. A limit switch reduces heat produced by the blower if the appliance gets overly warm. A furnace repair technician near you can adjust this limit switch so the blower remains warm.

If rooms located on the opposite end of the home fail to get sufficiently warm, the furnace blower may be undersized for your home, type of insulation, and outside weather conditions. In this case, you’ll need to have the furnace replaced.

furnace ductwork

When It’s the Ductwork and Not Furnace Repair

In some cases, the home’s ductwork may be at fault for a furnace not operating as it should. Layers of dust, dirt, pet hair and dander, and other debris slow down airflow through those ducts and affect the temperature of air as it moves through the home.

Connected sections of ductwork can also shift out of place or become dented and dinged over time, leading to cracks and leaks along their connectors or elsewhere. These leaks let out warm air as it flows through those ducts so that airflow to adjoining rooms is very weak. Before calling for residential furnace repair, have the home’s ducts checked for needed cleaning or replacement.

It’s also good to check the vents in each room and ensure they’re open and not blocked by furniture, curtains, or other items. Vacuum the front and back of the vents to remove dirt, dust, and other debris, to allow warm air to flow through properly.

Furnace Maintenance Tips

Maintaining your furnace throughout the year is an excellent way to ensure it functions as it should; neglecting routine maintenance is also an excellent way to have that furnace fail during cold winter months! Note a few residential furnace maintenance tips:

  • Change the furnace filter at least annually; if you have a central air conditioner, change the furnace filter twice per year, as cooled air is also run through that filter during summer months. A clogged furnace filter interferes with the temperature of air as it’s pushed through a home’s ductwork and can slow down airflow as well.
  • Open the front panel of the furnace and wipe down any dust and other debris clinging to its parts.
  • If you hear rattling noises coming from the furnace, note if any panels around the appliance need tightening. Loose panels allow air into the interior parts of the furnace, interfering with their operation.
  • Add a few drops of oil to the blower motor every year. You can find the blower motor oil ports by checking the furnace owner’s manual or an online diagram. Proper lubrication keeps the moving parts of the blower working as they should and reduces wear and tear on those parts.
  • Keep the area around the furnace free of dust, dirt, and other debris. A furnace can suck airborne particles into its inner components where they then clog the furnace filter, leading to excessive and early wear and tear.

How to Keep Your Home Warmer in Wintertime

Even if you have the best-quality furnace on the market, it’s still helpful to note a few additional steps that can help keep your home warmer in wintertime. These simple tips will also result in less wear and tear on your home’s furnace overall, potentially increasing its lifespan and resulting in fewer furnace repair costs.

  • Stone, concrete, tile, and timber flooring are often very cold, whereas carpet fibers hold warmth. If you prefer hardwood or stone floors versus interior carpeting, add thick area rugs in various rooms and especially in front of entryway doors and backrooms where your home is often coolest!
  • Thick drapes block cool air from coming in around drafty windows, keeping a home’s interior warmer in wintertime. It’s also good to add weather-stripping around old and drafty windows and even plastic sheeting outside those windows during the coldest winter months.
  • Check the condition of the home’s insulation on a regular basis and replace it as needed. Blown foam insulation will fill in cracks and leaks around exterior walls and elsewhere, keeping warm air inside the home and cold air out.
  • A roof helps to insulate the interior space so ensure your home’s roof is always in good repair. Replace missing or worn shingles as soon as possible and consider a roof coating or sealing to add a layer of insulation against outside cold.
  • Old windows often have etches and scratches along the exterior glass, letting in cold air. If you cannot afford to replace those windows, invest in thick window film that adds insulation along their surface.
  • Since heat rises, ceiling fans can help circulate heat back into your living space and keep your home warmer in wintertime. Don’t assume that ceiling fans are just for summertime but have some high-quality fans installed in your home and use them during winter as well.
  • Dry air is more difficult to heat than humid air, so consider installing a humidifier with the home’s furnace if needed. You can also purchase stand-alone humidifiers and place them in various rooms of the home for added moisture in the air.

Related Questions

How long should it take for a furnace to kick on?

When you adjust the thermostat of your home, it might take up to five minutes for it to read the surrounding temperature and then cycle on the furnace. However, if a furnace takes longer than five minutes to cycle on, have it or the thermostat checked for needed repairs.

What would cause a furnace not to kick on?

A dirty filter is one of the most common causes for a furnace to not kick on. Excess dirt and dust raises the temperature of a furnace so that the limit switch engages, and might also restrict airflow so that the motor or blower burns out. Change the filter at least annually to protect your furnace.

Why does a furnace pilot light keep going out?

The most common reasons for a pilot light to keep going out include a dirty valve and a drafty environment. Check the utility area of your home for drafts and clean the pilot light valve with a pipe cleaner. If these do not keep the pilot light engaged, call for residential furnace repair.

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