furnace repair

What to do When Your Furnace Will Not Switch On

It might feel overwhelming to troubleshoot your furnace when your heat won’t turn on. 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 fast and low-cost (or even free).

This checklist will walk you through how to fix your furnace when it won’t start, won’t stay on or won’t light.

When you need a pro in Litchfield Park, Cooler Tymes LLC can help.

We work on 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 evaluations often highlight a costly problem before it begins—and causes your HVAC system to fail.

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

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

Steps for Troubleshooting Your Furnace

Check Your Thermostat

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

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.
  • Confirm 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 override the program, change the temperature by using 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 thermostat to 5 degrees warmer than the room’s temperature.
Digital Thermostat

Your furnace should turn on 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 work immediately, your furnace may not have power.

If you’re utilizing a Wi-Fi thermostat—like one made by Nest, Ecobee, Lux, Honeywell or Bosch—check the manufacturer’s website for advice. If you can’t get your smart thermostat to work, call us at 623-208-6444 for help.

Smart Thermostat

Check Breakers and Switches

If you’ve already checked your thermostat, you will want to make sure your breakers and furnace switch are on.

  • Go 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 push the breaker to the “on” position. If the breaker trips and goes back to “off” after you do this, leave it alone. Contact a technician from Cooler Tymes LLC at 623-208-6444 immediately.

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 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 located 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 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 a very 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 placement depends upon what kind of furnace you have.

Replace furnace filter

When switching out your filter:

  • Shut off your furnace completely.
  • Pick up 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 damaging your system.

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 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 switch out your filter more often.

Check Out Your Condensate Pan

Condensate pans, or drain pans, hold 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 not blocked. 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 623-208-6444. You will probably need an updated pump.

Check Inside Your Furnace

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

Call us at 623-208-6444 if you see anything other than a steady, colored light or blinking green light. Your furnace is likely giving an error code that demands professional help.

Clean Your Flame Sensor

Is your furnace trying to start but shutting down without producing heat? A dirty 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 comfortable opening up your furnace. We can also do it for you.

Hoping to try 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 as well 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 wrong. Call us at 623-208-6444 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 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.
  • Move the knob to “pilot.”
  • Hold down the “reset” button as you move the flame of a long lighter to the pilot light opening.
  • Stop holding the “reset” button once the pilot light is lit.

Call us at 623-208-6444 if you’ve followed the instructions 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 623-208-6444 or use our online scheduler. We’ll come out to your home and figure out what’s wrong.

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