furnace repair

What to do When Your Furnace Refuses to Turn On

It might appear overwhelming to troubleshoot your furnace when your heat won’t work. 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 technical skills. And the majority of these fixes are quick and low-cost (or even free).

This list 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 Lake Forest, 1st Choice Heating & Air Conditioning, 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 often caused by forgotten routine maintenance. These checkups often highlight an expensive problem before it starts—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-maintained furnace often lasts longer and operates more efficiently, saving you more on your heating charges.

Ready to start troubleshooting your furnace? Follow our step-by-step guide below.

Steps for Troubleshooting Your Furnace

Inspect Your Thermostat

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

If you have a digital thermostat:

  • Change the batteries if the screen is off. 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.”
  • Look to see if the program is showing the correct day and time and is set to “run.” If you can’t alter the program, set the temperature by using the up/down arrows and press the “hold” button. This will compel 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 fairly quickly. If it doesn’t, see if it has power by pushing the fan switch from “auto” to “on.” If the fan doesn’t work instantly, 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 help. If you can’t get your smart thermostat to turn on, call us at 949-204-0859 for support.

Smart Thermostat

Check Breakers and Switches

If you’ve already checked your thermostat, 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.
  • Locate 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 pops back to “off” after you do this, leave it alone. Contact a professional from 1st Choice Heating & Air Conditioning, Inc. at 949-204-0859 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 get working 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 turn off too soon, due to dust in the filter restricting airflow.
  • Your energy bills could climb, because your furnace is turning on more often.
  • Your furnace may fail permantly faster, because it has to work harder.
  • Your furnace could lose power, because an excessively 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 placement depends upon what kind of furnace you have.

Replace furnace filter

When switching out your filter:

  • Shut down your furnace completely.
  • Pick up the filter, hold it up to the light and look through it. Replace it 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 less difficult 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 monthly. Pleated filters usually 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 switch out your filter on a more regular basis.

Inspect Your Condensate Pan

Condensate pans, or drain pans, catch water your furnace takes 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: 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: Check out the float switch. If the switch is “up” and there’s fluid in the pan, call us at 949-204-0859. You will probably need an updated pump.

Peek Inside Your Furnace

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

Call us at 949-204-0859 if you see anything other than a solid, colored light or blinking green light. Your furnace is likely giving an error code that requires professional assistance.

Clean Your Flame Sensor

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

Hoping 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 too if your gas valve is not electric.
  • Open 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.
  • Remount 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 replaced. Or something else could be the issue. Call us at 949-204-0859 for help if this happens.

Relight the Pilot Light

If your furnace is an older design, 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.

Reach out to us at 949-204-0859 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 949-204-0859 or use our online scheduler. We’ll come out to your home and find out what’s wrong.

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