furnace repair

What to do When Your Furnace Wont 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 may be able to avoid a furnace repair call with our DIY troubleshooting guide. You don’t need any mechanical skills. And most of these fixes are brief and inexpensive (or even free).

This guide 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 have to have a pro in Bossier City, Brooks Heating and Air Conditioning can help.

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 often caused by neglected routine maintenance. These evaluations often disclose a high-cost problem before it gets worse—and causes your HVAC system to break down.

During your appointment, our NATE-certified professionals will thoroughly inspect your furnace, make sure it’s operating 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 checking your thermostat. Is it telling your furnace to turn on?

If you have a digital thermostat:

  • Replace the batteries if the screen is blank. 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.”
  • Make sure the program is presenting the correct day and time and is set to “run.” If you can’t override the program, fix the temperature by pushing the up/down arrows and press the “hold” button. This will force the furnace to start if thermostat programming is causing complications.
  • Set the temp to 5 degrees warmer than the room’s temperature.
Digital Thermostat

Your furnace should start shortly. If it doesn’t, make sure it has power by sliding the fan switch from “auto” to “on.” If the fan doesn’t start immediately, your furnace may not be connected to power.

If you’re utilizing a Wi-Fi thermostat—like one made by Nest, Ecobee, Lux, Honeywell or Bosch—turn to the manufacturer’s website for guidelines. If you can’t get your smart thermostat to turn on, call us at 800-COOLING for help.

Smart Thermostat

Check Breakers and Switches

Next, 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 handling the panel or breakers.
  • Locate the breaker labeled “furnace” or “heat” and confirm that it’s switched in the “on” position. If the breaker has tripped, it will be in the center 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 a technician from Brooks Heating and Air Conditioning at 800-COOLING as soon as possible.

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 your furnace is located? 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 complications 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 climb, because your furnace is working more often.
  • Your furnace may have a shorter life span, because it has to work harder.
  • Your furnace could lose power, because an excessively dirty filter can cause 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 replacing your filter:

  • Shut off your furnace completely.
  • Grab the filter, hold it up to the light and look through it. Place a new filter in your system 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 simpler 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 once a month. Pleated filters generally 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 replace your filter on a more regular basis.

Check Out Your Condensate Pan

Condensate pans, or drain pans, catch 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: Check 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: Take a look at the float switch. If the switch is “up” and there’s liquid in the pan, call us at 800-COOLING. You will most likely need a new 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.

Reach out to us at 800-COOLING 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 generating heat? A filthy flame sensor could be to blame. 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.

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 turn off the power. Shut off the gas as well if your gas valve is not electric.
  • Remove 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 as usual. If it doesn’t start, the sensor might need to be updated. Or something else could be wrong. Call us at 800-COOLING for assistance if this happens.

Relight the Pilot Light

If your furnace is an older style, its pilot light could be out. 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 move the flame of a long lighter to the pilot light opening.
  • Release the “reset” button once the pilot light is lit.

Contact us at 800-COOLING if you’ve followed the guide twice and the pilot won’t light or stay lit.

Check Your Fuel Source

Are other gas appliances working? 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 turn on?

Call us today at 800-COOLING or use our online scheduler. We’ll come out to your home and find out what’s wrong.

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