furnace repair

What to do When Your Furnace Refuses to Start

It might seem scary to troubleshoot your furnace when your heat won’t work. 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 the majority of these fixes are quick 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 require a pro in Mankato area, Northern Comfort Inc can be there.

We service most makes and models of furnaces. If you need a new heating system, we also offer furnace replacement and furnace installation.

Furnace breakdowns are generally caused by neglected routine maintenance. These evaluations often reveal a costly problem before it gets worse—and causes your HVAC system to fail.

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

If you have a digital thermostat:

  • Switch out the batteries if the screen is off. If the digital screen is scrambled, you may need to replace your thermostat.
  • See if that the switch is set to “heat” instead of “off” or “cool.”
  • Find out if the program is displaying the right 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 force the furnace to turn on if thermostat programming is causing complications.
  • Set the temperature to 5 degrees warmer than the room’s temperature.
Digital Thermostat

Your furnace should kick on within a few minutes. If it doesn’t, see if it has power by moving the fan switch from “auto” to “on.” If the fan doesn’t run right away, 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—refer to the manufacturer’s website for guidelines. If you can’t get your smart thermostat to turn on, call us at 507-307-4818 for assistance.

Smart Thermostat

Check Breakers and Switches

Next, 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 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 middle or “off” position.
  • With one hand, firmly shift the breaker to the “on” position. If the breaker trips and moves back to “off” after you do this, leave it alone. Contact a technician from Northern Comfort Inc at 507-307-4818 right away.

Your furnace has at least one wall switch located 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 start if the switch was off. (Not sure where to find your furnace? Look in your basement, garage or utility closet. It could also be placed 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 stop working too soon, due to dust in the filter hampering airflow.
  • Your energy bills could increase, 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 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 position depends upon what model 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. 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 hurting your machine.

To make the process easier for yourself, 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 work for about 10 years.

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

Look at Your Condensate Pan

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

Follow these steps if your furnace is leaking 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 507-307-4818. You will probably need an updated pump.

Look Inside Your Furnace

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

Contact us at 507-307-4818 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 assistance.

Clean Your Flame Sensor

Is your furnace making an effort to start but shutting down without generating heat? A soiled flame sensor could be be the reason. When this takes place, 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.

Ready 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 switch off the power. Shut off the gas also if your gas valve is not electric.
  • Open 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.
  • 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 regularly. If it doesn’t kick on, the sensor might need to be updated. Or something else could be the problem. Call us at 507-307-4818 for guidance if this happens.

Relight the Pilot Light

If your furnace is an older model, its pilot light could be blown out. 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.
  • Switch 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.

Call us at 507-307-4818 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 start?

Call us today at 507-307-4818 or use our online scheduler. We’ll come out to your home and find out what’s wrong.

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