furnace repair

What to do When Your Furnace Refuses to Start

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

You might be able to bypass 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 checklist 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 Wheeling, Local HVAC Repair & Service 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 forgotten routine maintenance. These service appointments often disclose a high-cost problem before it starts—and causes your HVAC system to fail.

During this service, our NATE-certified professionals will closely inspect your furnace, make sure it’s operating properly and lubricate moving parts. A well-maintained 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

Inspect Your Thermostat

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

If you have a digital thermostat:

  • Replace the batteries if the screen is unresponsive. If the digital screen is scrambled, you may need to replace your thermostat.
  • Confirm that the switch is set to “heat” instead of “off” or “cool.”
  • Look to see if the program is presenting the right day and time and is set to “run.” If you can’t override the program, change 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 within a few minutes. If it doesn’t, see if 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—turn to the manufacturer’s website for help. If you can’t get your smart thermostat to turn on, call us at 224-300-4806 for assistance.

Smart Thermostat

Check Breakers and Switches

Next, you will want 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 touching 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 middle or “off” position.
  • With one hand, firmly push the breaker to the “on” position. If the breaker trips and moves back to “off” after you do this, leave it alone. Contact a professional from Local HVAC Repair & Service at 224-300-4806 right away.

Your furnace has at least one wall switch situated 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 your furnace is located? Look in your basement, garage or utility closet. It could also be placed in a crawl space or attic.)

Replace Your Air Filter

Dirty, clogged air filters often generate 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 climb, because your furnace is working 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 find your air filter inside your furnace’s blower component, attached filter case or wall-mounted return air grille. Its location depends upon what kind of furnace you have.

Replace furnace filter

When replacing your filter:

  • Turn off your furnace completely.
  • Pull out 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.
  • Replace the new filter with the arrow pointing toward the furnace to avoid damaging your system.

To make the process simpler next time, use a permanent marker on your furnace housing or ductwork to indicate the airflow direction and filter size.

We advise replacing flat filters each month. 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 frequently.

Inspect Your Condensate Pan

Condensate pans, or drain pans, catch 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: 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: Find the float switch. If the switch is “up” and there’s fluid in the pan, call us at 224-300-4806. You will likely need a more modern pump.

Look Inside Your Furnace

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

Reach out to us at 224-300-4806 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 making an effort to start but shutting down without producing heat? A soiled 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 comfortable opening up your furnace. We can also do it for you.

Want 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.
  • 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.
  • 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 as usual. If it doesn’t kick on, the sensor might need to be replaced. Or something else could be the problem. Call us at 224-300-4806 for help 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.
  • 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.

Reach out to us at 224-300-4806 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 start?

Call us today at 224-300-4806 or use our online scheduler. We’ll come out to your home and find out what’s wrong.

*Required fields