furnace repair

What to do When Your Furnace Will Not Start

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 industry skills. And most 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 need a pro in Macon, Air Temperature Control can be there.

We repair and maintain most makes and models of furnaces. If you need a new heating system, we also offer furnace replacement and furnace installation.

Furnace breakdowns are usually caused by a lack of routine maintenance. These checkups often reveal an expensive problem before it starts—and causes your HVAC system to stop working.

During our visit, our NATE-certified professionals will carefully 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 charges.

Ready to tackle 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:

  • Replace the batteries if the screen is off. If the digital screen is scrambled, you may need a new thermostat.
  • Check that that the switch is set to “heat” instead of “off” or “cool.”
  • Make sure the program is displaying the right day and time and is set to “run.” If you can’t change the program, change the temperature with the up/down arrows and press the “hold” button. This will compel 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 kick on fairly quickly. If it doesn’t, double check that it has power by sliding the fan switch from “auto” to “on.” If the fan doesn’t run immediately, your furnace may not have power.

If you’re using 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 work, call us at 478-202-3170 for support.

Smart Thermostat

Check Breakers and Switches

Next, 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.
  • Find 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 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 technician from Air Temperature Control at 478-202-3170 immediately.

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 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 cause 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 working more often.
  • Your furnace may not last as long, because it has to work harder.
  • Your furnace could lose power, because an excessively dirty filter can prompt the breaker to trip.

You can locate 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 switching out your filter:

  • Shut off your furnace completely.
  • Pull out 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 hurting your machine.

To make the process less difficult in the future, use a permanent marker on your furnace housing or ductwork to indicate the airflow direction and filter size.

We advise replacing flat filters monthly. 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 change your filter on a more regular basis.

Inspect Your Condensate Pan

Condensate pans, or drain pans, capture water your furnace removes 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 clear. 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 fluid in the pan, call us at 478-202-3170. You will most likely need a new 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 kind, this light could be placed on the outside of your furnace.

Call us at 478-202-3170 if you see anything other than a steady, colored light or blinking green light. Your furnace is likely giving an error code that requires professional service.

Clean Your Flame Sensor

Is your furnace attempting to start but turning off without producing heat? A dirty flame sensor could be to blame. When this happens, your furnace will try to turn 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 switch off the power. Shut off the gas also 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 regularly. If it doesn’t kick on, the sensor might need to be switched out for a new one. Or something else could be the issue. Call us at 478-202-3170 for guidance 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 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 bring 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 478-202-3170 if you’ve followed the steps 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 start?

Call us today at 478-202-3170 or use our online scheduler. We’ll come out to your home and identify what’s wrong.

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