furnace repair

What to do When Your Furnace Wont Turn On

It might feel overwhelming to troubleshoot your furnace when your heat won’t run. But it doesn’t have to be that way.

You could be able to bypass a furnace repair call with our DIY troubleshooting guide. You don’t need any mechanical skills. And many of these fixes are fast and low-cost (or even free).

This guide 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 have to have a pro in Colorado Springs, Mitchell Heating can help.

We work on most makes and models of furnaces. If you need an updated heating system, we also offer furnace replacement and furnace installation.

Furnace breakdowns are generally caused by forgotten routine maintenance. These service appointments often disclose a costly problem before it starts—and causes your HVAC system to break down.

During your appointment, 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 charges.

Ready to begin 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 turn on?

If you have a digital thermostat:

  • Switch out the batteries if the screen is blank. If the digital screen is scrambled, you may need a different thermostat.
  • Check that that the switch is set to “heat” instead of “off” or “cool.”
  • Find out if the program is presenting the right day and time and is set to “run.” If you can’t alter the program, set the temperature by pushing the up/down arrows and press the “hold” button. This will compel the furnace to switch on if thermostat programming is causing complications.
  • Set the temp to 5 degrees warmer than the room’s temperature.
Digital Thermostat

Your furnace should kick on fairly quickly. If it doesn’t, see if it has power by sliding the fan switch from “auto” to “on.” If the fan doesn’t work immediately, 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—refer to the manufacturer’s website for advice. If you can’t get your smart thermostat to function properly, call us at 719-422-4236 for assistance.

Smart Thermostat

Check Breakers and Switches

Next, you will need 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 working with the panel or breakers.
  • Find 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 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 an expert from Mitchell Heating at 719-422-4236 right away.

Your furnace has at least one wall switch located 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 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, clogged air filters often create complications that are easily avoidable.

  • Your furnace can overheat and stop working 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 an extra 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 location depends upon what kind of furnace you have.

Replace furnace filter

When switching out your filter:

  • Turn off your furnace completely.
  • Pull out 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 damaging your system.

To make the process simpler 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 monthly. 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 switch out your filter on a more regular basis.

Look at Your Condensate Pan

Condensate pans, or drain pans, catch water your furnace takes 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 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: Take a look at the float switch. If the switch is “up” and there’s fluid in the pan, call us at 719-422-4236. You will likely need a more modern pump.

Peek Inside Your Furnace

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

Call us at 719-422-4236 if you see anything other than a solid, colored light or blinking green light. Your furnace could be giving an error code that needs professional help.

Clean Your Flame Sensor

Is your furnace attempting to start but turning off without blowing heat? A dirty flame sensor could be to blame. When this occurs, your furnace will try to switch 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.

Ready 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 shut off the power. Shut off the gas as well 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 normally. If it doesn’t start, the sensor might need to be replaced. Or something else could be the problem. Call us at 719-422-4236 for assistance if this happens.

Relight the Pilot Light

If your furnace is an older design, its pilot light could be extinguished. Relight it following the instructions on the label. You can find 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 719-422-4236 if you’ve followed the steps 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 719-422-4236 or use our online scheduler. We’ll come out to your home and identify what’s wrong.

*Required fields