furnace repair

What to do When Your Furnace Will Not Turn On

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

You may 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 list 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 need a pro in Marshfield, House of Heating Incorporated can lend a hand.

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

Furnace breakdowns are often caused by a lack of routine maintenance. These service appointments often reveal an expensive problem before it gets worse—and causes your HVAC system to break down.

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

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

Steps for Troubleshooting Your Furnace

Inspect Your Thermostat

Start by examining your thermostat. Is it telling your furnace to switch on?

If you have a digital thermostat:

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

Your furnace should start shortly. If it doesn’t, make sure it has power by pushing the fan switch from “auto” to “on.” If the fan doesn’t work instantly, your furnace may not be connected to power.

If you’re connected to 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 function properly, call us at 888-384-3163 for assistance.

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 make sure that it’s switched in the “on” position. If the breaker has tripped, it will be in the center or “off” position.
  • With one hand, firmly push the breaker to the “on” position. If the breaker trips and pops back to “off” after you do this, leave it alone. Contact an expert from House of Heating Incorporated at 888-384-3163 immediately.

Your furnace has at least one wall switch situated on or near it—no matter its age or brand.

  • This switch should be flipped up in the “on” position. It can take your furnace up to five minutes to kick on 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 create issues that are easily avoidable.

  • Your furnace can overheat and stop working too soon, due to dust in the filter restricting airflow.
  • Your energy bills could increase, because your furnace is starting up more often.
  • Your furnace may fail permantly faster, because it has to work harder.
  • Your furnace could lose power, because an excessively dirty filter can prompt 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 model of furnace you have.

Replace furnace filter

When replacing your filter:

  • Shut off your furnace completely.
  • Pick up the filter, hold it up to the light and look through it. Place a new filter in your system 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 easier in the future, use a permanent marker on your furnace housing or ductwork to indicate the airflow direction and filter size.

We suggest replacing flat filters monthly. Pleated filters typically 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, capture water your furnace takes 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 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: Check out the float switch. If the switch is “up” and there’s water in the pan, call us at 888-384-3163. You will most likely need a new pump.

Peek Inside Your Furnace

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

Contact us at 888-384-3163 if you see anything other than a steady, colored light or blinking green light. Your furnace could be giving an error code that demands professional help.

Clean Your Flame Sensor

Is your furnace attempting to start but shutting off without producing heat? A filthy flame sensor could be be the reason. When this occurs, 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 switch off the power. Shut off the gas as well if your gas valve is not electric.
  • Remove 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 normally. If it doesn’t turn on, the sensor might need to be updated. Or something else could be wrong. Call us at 888-384-3163 for help if this happens.

Relight the Pilot Light

If your furnace is an older design, its pilot light could be extinguished. 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.
  • Move the knob to “pilot.”
  • Hold down the “reset” button as you deliver the flame of a long lighter to the pilot light opening.
  • Release the “reset” button once the pilot light is lit.

Contact us at 888-384-3163 if you’ve followed the guide twice and the pilot won’t light or stay lit.

Check Your Fuel Source

Are other gas appliances operating? 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 888-384-3163 or use our online scheduler. We’ll come out to your home and find out what’s wrong.

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