furnace repair

What to do When Your Furnace Wont Start

It might seem 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 industry skills. And the majority of these fixes are brief and affordable (or even free).

This list 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 require a pro in Franklin Lakes, Total Comfort can help.

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 generally caused by forgotten routine maintenance. These service appointments often reveal a costly problem before it gets worse—and causes your HVAC system to stop working.

During this service, 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 bill.

Ready to start 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 switch on?

If you have a digital thermostat:

  • Switch out the batteries if the screen is unresponsive. If the digital screen is scrambled, you may need to replace your thermostat.
  • See if that the switch is set to “heat” instead of “off” or “cool.”
  • Make sure the program is showing the correct day and time and is set to “run.” If you can’t change the program, fix the temperature by pushing the up/down arrows and press the “hold” button. This will compel the furnace to turn on if thermostat programming is causing an issue.
  • Set the thermostat to 5 degrees warmer than the room’s temperature.
Digital Thermostat

Your furnace should start shortly. If it doesn’t, see if it has power by moving the fan switch from “auto” to “on.” If the fan doesn’t start right away, 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 work, call us at 201-268-5663 for help.

Smart Thermostat

Check Breakers and Switches

Next, you will need 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.
  • Pinpoint 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 midpoint or “off” position.
  • With one hand, firmly shift 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 Total Comfort at 201-268-5663 as soon as possible.

Your furnace has at least one wall switch situated 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 your furnace is located? Look in your basement, garage or utility closet. It could also be in a crawl space or attic.)

Replace Your Air Filter

Dirty, blocked air filters often create complications that are easily avoidable.

  • Your furnace can overheat and shut down too soon, due to dust in the filter diminishing airflow.
  • Your energy bills could get more expensive, because your furnace is turning on 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 cause 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 type of furnace you have.

Replace furnace filter

When replacing your filter:

  • Shut down 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.
  • Put in the new filter with the arrow pointing toward the furnace to avoid damage.

To make the process easier 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 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 change your filter on a more regular basis.

Look at Your Condensate Pan

Condensate pans, or drain pans, catch water your furnace pulls 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 water in the pan, call us at 201-268-5663. You will probably need an updated pump.

Check Inside Your Furnace

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

Contact us at 201-268-5663 if you see anything other than a steady, colored light or blinking green light. Your furnace is probably giving an error code that demands professional assistance.

Clean Your Flame Sensor

Is your furnace attempting to start but shutting off without producing heat? A soiled flame sensor could be to blame. When this takes place, 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 alright opening up your furnace. We can also do it for you.

Want 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.
  • Take off your furnace’s front panel and trace 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 kick on, the sensor might need to be replaced. Or something else could be the problem. Call us at 201-268-5663 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.

Reach out to us at 201-268-5663 if you’ve followed the guide 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 start?

Call us today at 201-268-5663 or use our online scheduler. We’ll come out to your home and figure out what’s wrong.

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