furnace repair

What to do When Your Furnace Refuses to Switch On

It might seem scary to troubleshoot your furnace when your heat won’t work. But it doesn’t have to be that way.

You might be able to avoid a furnace repair call with our DIY troubleshooting guide. You don’t need any technical skills. And most of these fixes are quick and low-cost (or even free).

This guide will walk you through how to fix your furnace when it won’t switch on, won’t stay on or won’t light.

When you require a pro in Manassas, Air-Right Energy Design, Inc. can be there.

We repair and maintain most makes and models of furnaces. If you need a more modern heating system, we also offer furnace replacement and furnace installation.

Furnace breakdowns are often caused by neglected routine maintenance. These evaluations often highlight a costly problem before it begins—and causes your HVAC system to break down.

During our visit, our NATE-certified professionals will thoroughly inspect your furnace, make sure it’s working properly and lubricate moving parts. A well-kept furnace often lasts longer and operates more efficiently, saving you more on your heating charges.

Ready to begin troubleshooting your furnace? Follow our step-by-step guide below.

Steps for Troubleshooting Your Furnace

Take a Look at Your Thermostat

Start by checking your thermostat. Is it telling your furnace to start?

If you have a digital thermostat:

  • Change the batteries if the screen is unresponsive. If the digital screen is scrambled, you may need a new thermostat.
  • Check that that the switch is set to “heat” instead of “off” or “cool.”
  • Find out if the program is presenting the correct day and time and is set to “run.” If you can’t override the program, fix the temperature with the up/down arrows and press the “hold” button. This will compel the furnace to start if thermostat programming is causing complications.
  • Set the thermostat to 5 degrees warmer than the room’s temperature.
Digital Thermostat

Your furnace should turn on within a few minutes. If it doesn’t, double check that it has power by moving the fan switch from “auto” to “on.” If the fan doesn’t run right away, your furnace may not have power.

If you’re connected to a Wi-Fi thermostat—like one made by Nest, Ecobee, Lux, Honeywell or Bosch—turn to the manufacturer’s website for help. If you can’t get your smart thermostat to function properly, call us at 703-260-1148 for help.

Smart Thermostat

Check Breakers and Switches

After that, you will want to make sure your breakers and furnace switch are on.

  • Go to your house’s main electrical panel. It’s the gray metal box on the wall in your basement, garage or closet.
  • Dry off your hands and feet before handling the panel or breakers.
  • Pinpoint the breaker labeled “furnace” or “heat” and double-check that it’s switched in the “on” position. If the breaker has tripped, it will be in the middle or “off” position.
  • With one hand, firmly shift the breaker to the “on” position. If the breaker trips and moves back to “off” after you do this, leave it alone. Contact a technician from Air-Right Energy Design, Inc. at 703-260-1148 immediately.

Your furnace has at least one wall switch placed on or near it—no matter how old it is or who made it.

  • This switch should be flipped up in the “on” position. It can take your furnace up to five minutes to get working if the switch was off. (Not sure where to find your furnace? Look in your basement, garage or utility closet. It could also be placed in a crawl space or attic.)

Replace Your Air Filter

Dirty, blocked air filters often cause issues that are easily avoidable.

  • Your furnace can overheat and shut down too soon, due to dust in the filter diminishing airflow.
  • Your energy bills could increase, because your furnace is working more often.
  • Your furnace may have a shorter life span, because it has to work harder.
  • Your furnace could lose power, because an excessively dirty filter can cue the breaker to trip.

You can get to your air filter inside your furnace’s blower component, attached filter case or wall-mounted return air grille. Its placement depends upon what kind of furnace you have.

Replace furnace filter

When changing out your filter:

  • Shut down your furnace completely.
  • Pick up the filter, hold it up to the light and look through it. Replace it if you can’t see light through it.
  • Replace the new filter with the arrow pointing toward the furnace to avoid damage.

To make the process easier for yourself, use a permanent marker on your furnace housing or ductwork to indicate the airflow direction and filter size.

We recommend replacing flat filters once a month. Pleated filters usually last about three months. You can also get a washable filter that will be good for about 10 years.

If you have children or pets, you may need to switch out your filter more often.

Check Out Your Condensate Pan

Condensate pans, or drain pans, catch water your furnace pulls from the air.

Follow these steps if your furnace is seeping water or there’s standing water in the pan.

  • If your pan has a PVC pipe/drain: Make sure that it’s not blocked. If it’s not, you can use a special pan-cleaning tablet from a home improvement or hardware store.
  • If your pan has a pump: Find the float switch. If the switch is “up” and there’s liquid in the pan, call us at 703-260-1148. You will most likely need a more modern pump.

Check Inside Your Furnace

You can check the condition of your furnace’s blower motor by checking inside the plastic window. Depending on the kind, this light could be located on the outside of your furnace.

Reach out to us at 703-260-1148 if you see anything other than a solid, colored light or blinking green light. Your furnace could be giving an error code that requires professional assistance.

Clean Your Flame Sensor

Is your furnace trying to start but shutting off without blowing heat? A soiled flame sensor could be to blame. When this happens, your furnace will try to turn on three times. Then, a safety feature will shut it down for about an hour.

You can clean the flame sensor yourself if you feel alright opening up your furnace. We can also do it for you.

Hoping to try cleaning the sensor yourself? You’ll need the following:

  • A 1/4” hex screwdriver or wrench
  • Piece of light-grit sandpaper, steel wool or emery cloth
  • A dry, clean paper towel

Next:

  • Use your furnace’s wall switch or breaker to shut off the power. Shut off the gas also if your gas valve is not electric.
  • Remove your furnace’s front panel and trace the wire to the flame sensor, which looks like a thin, bent rod.
  • Unscrew the rod and use your sandpaper, steel wool or emery cloth to gently clean the metal rod.
  • Use a paper towel to wipe off the rod.
  • Remount the sensor.
  • Put your furnace’s doors back on.
  • Turn the furnace’s power back on. Your furnace may run through a series of checks before it starts normally. If it doesn’t kick on, the sensor might need to be switched out for a new one. Or something else could be the problem. Call us at 703-260-1148 for assistance if this happens.

Relight the Pilot Light

If your furnace is an older style, its pilot light could be out. Relight it following the instructions on the label. You can locate the label on your furnace’s doors.

Or you can follow these steps:

  • Locate the switch on the bottom of your furnace labeled “pilot,” “on” and “off.”
  • Rotate the switch to the “off” position.
  • Wait at least five minutes. This avoids the possibility of starting a fire.
  • Turn the knob to “pilot.”
  • Hold down the “reset” button as you move the flame of a long lighter to the pilot light opening.
  • Stop holding the “reset” button once the pilot light is lit.

Call us at 703-260-1148 if you’ve followed the instructions twice and the pilot won’t light or stay lit.

Check Your Fuel Source

Are other gas appliances functioning? If they’re not, your natural gas service could be off. Or you could be out of propane.

We Can Diagnose Furnace Problems

Made it through our troubleshooting guide but your furnace still won’t turn on?

Call us today at 703-260-1148 or use our online scheduler. We’ll come out to your home and find out what’s wrong.

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