furnace repair

What to do When Your Furnace Wont Switch On

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

You could be able to skip a furnace repair call with our DIY troubleshooting guide. You don’t need any mechanical skills. And most of these fixes are fast and affordable (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 have to have a pro in Erie, Patterson & Stirling Inc can be there.

We service 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 a lack of routine maintenance. These checkups often disclose a costly problem before it starts—and causes your HVAC system to fail.

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

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

Steps for Troubleshooting Your Furnace

Take a Look at Your Thermostat

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

If you have a digital thermostat:

  • Replace the batteries if the screen is blank. 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 displaying the current day and time and is set to “run.” If you can’t alter the program, set the temperature with the up/down arrows and press the “hold” button. This will compel the furnace to start 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 fairly quickly. 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 access 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 turn on, call us at 814-308-0416 for help.

Smart Thermostat

Check Breakers and Switches

Next, 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.
  • Locate the breaker labeled “furnace” or “heat” and confirm 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 goes back to “off” after you do this, leave it alone. Contact a technician from Patterson & Stirling Inc at 814-308-0416 immediately.

Your furnace has at least one wall switch situated 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 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 in a crawl space or attic.)

Replace Your Air Filter

Dirty, closed off air filters often create problems that are easily avoidable.

  • Your furnace can overheat and turn off too soon, due to dust in the filter hampering airflow.
  • Your energy bills could increase, because your furnace is turning on more often.
  • Your furnace may not last as long, because it has to work harder.
  • Your furnace could lose power, because an excessively dirty filter can cause the breaker to trip.

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

Replace furnace filter

When replacing 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 hurting your machine.

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 each month. 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 replace your filter more frequently.

Look at 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: Be sure that it’s clear. 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: Take a look at the float switch. If the switch is “up” and there’s water in the pan, call us at 814-308-0416. You will likely need a new pump.

Look Inside Your Furnace

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

Call us at 814-308-0416 if you see anything other than a stable, colored light or blinking green light. Your furnace is likely giving an error code that needs professional service.

Clean Your Flame Sensor

Is your furnace making an effort to start but shutting down without generating heat? A filthy flame sensor could be at fault. 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 take on 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 too if your gas valve is not electric.
  • Open your furnace’s front panel and follow 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.
  • Put back 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 the problem. Call us at 814-308-0416 for help if this happens.

Relight the Pilot Light

If your furnace is an older style, its pilot light could be blown 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 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 814-308-0416 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 work?

Call us today at 814-308-0416 or use our online scheduler. We’ll come out to your home and find out what’s wrong.

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