furnace repair

What to do When Your Furnace Will Not Start

It might feel 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 fast 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 require a pro in Greensburg, Wallpe Heating & Cooling can be there.

We work on 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 generally caused by forgotten routine maintenance. These checkups often highlight a costly problem before it gets worse—and causes your HVAC system to break down.

During this service, our NATE-certified professionals will carefully inspect your furnace, make sure it’s working 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

Check Your Thermostat

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

If you have a digital thermostat:

  • Switch out the batteries if the screen is unresponsive. If the digital screen is scrambled, you may need a different 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 override the program, set the temperature by using 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 temp to 5 degrees warmer than the room’s temperature.
Digital Thermostat

Your furnace should kick on 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 work right away, 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—turn to the manufacturer’s website for help. If you can’t get your smart thermostat to function properly, call us at 812-638-4232 for assistance.

Smart Thermostat

Check Breakers and Switches

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

  • Head 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 midpoint 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 an expert from Wallpe Heating & Cooling at 812-638-4232 right away.

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 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, blocked air filters often cause problems that are easily avoidable.

  • Your furnace can overheat and turn off too soon, due to dust in the filter diminishing airflow.
  • Your energy bills could climb, 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 a very 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 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. Get a new filter if you can’t see light through it.
  • Put in the new filter with the arrow pointing toward the furnace to avoid damaging your system.

To make the process less difficult 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 each month. Pleated filters generally 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 frequently.

Check Out Your Condensate Pan

Condensate pans, or drain pans, capture water your furnace pulls 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 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 fluid in the pan, call us at 812-638-4232. You will probably need an updated pump.

Look Inside Your Furnace

You can check the status 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.

Reach out to us at 812-638-4232 if you see anything other than a solid, colored light or blinking green light. Your furnace could be giving an error code that demands professional service.

Clean Your Flame Sensor

Is your furnace attempting to start but turning off without producing heat? A soiled flame sensor could be at fault. When this happens, your furnace will try to start 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 tackle 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 as well if your gas valve is not electric.
  • Take off 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.
  • Replace 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 switched out for a new one. Or something else could be the problem. Call us at 812-638-4232 for guidance 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 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.
  • Stop holding the “reset” button once the pilot light is lit.

Call us at 812-638-4232 if you’ve followed the steps 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 work?

Call us today at 812-638-4232 or use our online scheduler. We’ll come out to your home and identify what’s wrong.

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