furnace repair

What to do When Your Furnace Refuses to Turn 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 might be able to skip a furnace repair call with our DIY troubleshooting guide. You don’t need any mechanical skills. And many 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 Cedar Rapids, Ilten's Incorporated 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 generally caused by forgotten routine maintenance. These evaluations often disclose an expensive problem before it begins—and causes your HVAC system to stop working.

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

Ready to begin 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:

  • Change the batteries if the screen is unresponsive. If the digital screen is scrambled, you may need a new thermostat.
  • See if that the switch is set to “heat” instead of “off” or “cool.”
  • Look to see if the program is presenting the current day and time and is set to “run.” If you can’t change the program, fix the temperature by pushing the up/down arrows and press the “hold” button. This will force the furnace to turn on if thermostat programming is causing a problem.
  • 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 pushing the fan switch from “auto” to “on.” If the fan doesn’t work 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—refer to the manufacturer’s website for advice. If you can’t get your smart thermostat to turn on, call us at 319-208-3295 for help.

Smart Thermostat

Check Breakers and Switches

After that, you will need 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 working with 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 move 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 Ilten's Incorporated at 319-208-3295 right away.

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 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, blocked air filters often generate issues 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 get more expensive, because your furnace is starting up 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 position depends upon what model of furnace you have.

Replace furnace filter

When replacing your filter:

  • Shut 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.
  • Replace the new filter with the arrow pointing toward the furnace to avoid damage.

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 once a month. Pleated filters generally 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 replace your filter more often.

Check Out Your Condensate Pan

Condensate pans, or drain pans, hold water your furnace removes 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: Find the float switch. If the switch is “up” and there’s liquid in the pan, call us at 319-208-3295. You will probably need a more modern pump.

Look Inside Your Furnace

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

Call us at 319-208-3295 if you see anything other than a stable, colored light or blinking green light. Your furnace could be giving an error code that needs professional assistance.

Clean Your Flame Sensor

Is your furnace making an effort to start but turning off without producing heat? A soiled flame sensor could be be the reason. When this occurs, 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 confident opening up your furnace. We can also do it for you.

Want 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 also if your gas valve is not electric.
  • Remove 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 as usual. If it doesn’t kick on, the sensor might need to be replaced. Or something else could be wrong. Call us at 319-208-3295 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.
  • Move the knob to “pilot.”
  • Hold down the “reset” button as you move the flame of a long lighter to the pilot light opening.
  • Release the “reset” button once the pilot light is lit.

Call us at 319-208-3295 if you’ve followed the instructions 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 319-208-3295 or use our online scheduler. We’ll come out to your home and find out what’s wrong.

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