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 run. 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 mechanical skills. And many of these fixes are brief and affordable (or even free).

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

When you have to have a pro in Midlothian, Daniel's Heating & Refrigeration Corp. can lend a hand.

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 stop working.

During this service, our NATE-certified professionals will carefully 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 bill.

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 looking at your thermostat. Is it telling your furnace to turn on?

If you have a digital thermostat:

  • Change the batteries if the screen is off. If the digital screen is scrambled, you may need a new thermostat.
  • Confirm that the switch is set to “heat” instead of “off” or “cool.”
  • Make sure the program is displaying the current day and time and is set to “run.” If you can’t change the program, fix the temperature with the up/down arrows and press the “hold” button. This will require the furnace to switch on if thermostat programming is causing complications.
  • Set the thermostat to 5 degrees warmer than the room’s temperature.
Digital Thermostat

Your furnace should start within a few minutes. If it doesn’t, make sure it has power by sliding the fan switch from “auto” to “on.” If the fan doesn’t run instantly, your furnace may not have power.

If you’re utilizing a Wi-Fi thermostat—like one made by Nest, Ecobee, Lux, Honeywell or Bosch—check the manufacturer’s website for advice. If you can’t get your smart thermostat to work, call us at 804-372-0313 for help.

Smart Thermostat

Check Breakers and Switches

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

  • Find 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 working with the panel or breakers.
  • Locate 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 pops back to “off” after you do this, leave it alone. Contact a professional from Daniel's Heating & Refrigeration Corp. at 804-372-0313 right away.

Your furnace has at least one wall switch placed on or near it—no matter when it was made or who manufactured it.

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

Replace Your Air Filter

Dirty, closed off air filters often generate problems 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 climb, because your furnace is starting up 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 position depends upon what type of furnace you have.

Replace furnace filter

When changing out your filter:

  • Turn off your furnace completely.
  • Grab the filter, hold it up to the light and look through it. Replace it if you can’t see light through it.
  • Install the new filter with the arrow pointing toward the furnace to avoid damaging your system.

To make the process simpler 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 monthly. Pleated filters typically last about three months. You can also get a washable filter that will last about 10 years.

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

Check Out Your Condensate Pan

Condensate pans, or drain pans, capture water your furnace removes from the air.

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

  • If your pan has a PVC pipe/drain: Be sure that it’s open. 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 804-372-0313. You will likely need a more modern pump.

Look Inside Your Furnace

You can check the quality of your furnace’s blower motor by looking inside the plastic window. Depending on the model, this light could be somewhere on the outside of your furnace.

Contact us at 804-372-0313 if you see anything other than a solid, colored light or blinking green light. Your furnace could be giving an error code that needs professional help.

Clean Your Flame Sensor

Is your furnace attempting to start but shutting down without generating heat? A dirty flame sensor could be to blame. When this happens, your furnace will try to switch 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 comfortable opening up your furnace. We can also do it for you.

Want 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 switch off the power. Shut off the gas also if your gas valve is not electric.
  • Take off your furnace’s front panel and track 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 as usual. If it doesn’t turn on, the sensor might need to be updated. Or something else could be the issue. Call us at 804-372-0313 for assistance if this happens.

Relight the Pilot Light

If your furnace is an older style, its pilot light could be extinguished. Relight it following the instructions on the label. You can read 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.
  • Move the knob to “pilot.”
  • Hold down the “reset” button as you deliver the flame of a long lighter to the pilot light opening.
  • Let go of the “reset” button once the pilot light is lit.

Contact us at 804-372-0313 if you’ve followed the guide 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 804-372-0313 or use our online scheduler. We’ll come out to your home and identify what’s wrong.

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