furnace repair

What to do When Your Furnace Wont Start

It might appear scary to troubleshoot your furnace when your heat won’t run. 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 technical skills. And the majority of these fixes are brief and inexpensive (or even free).

This list 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 Rapid City, Street Heating & Sheet Metal Inc can lend a hand.

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

Furnace breakdowns are often caused by a lack of routine maintenance. These checkups often highlight an expensive problem before it starts—and causes your HVAC system to break down.

During this service, our NATE-certified professionals will closely inspect your furnace, make sure it’s operating properly and lubricate moving parts. A well-kept 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

Take a Look at 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 blank. If the digital screen is scrambled, you may need to replace your thermostat.
  • Check that that the switch is set to “heat” instead of “off” or “cool.”
  • Look to see if the program is displaying the current day and time and is set to “run.” If you can’t override the program, set the temperature by using the up/down arrows and press the “hold” button. This will require the furnace to switch on if thermostat programming is causing complications.
  • Set the thermostat to 5 degrees warmer than the room’s temperature.
Digital Thermostat

Your furnace should start fairly quickly. If it doesn’t, see if it has power by sliding the fan switch from “auto” to “on.” If the fan doesn’t work right away, your furnace may not have 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 function properly, call us at 605-342-5107 for support.

Smart Thermostat

Check Breakers and Switches

Next, you will want to make sure your breakers and furnace switch are on.

  • Find 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 double-check 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 shift the breaker to the “on” position. If the breaker trips and goes back to “off” after you do this, leave it alone. Contact an expert from Street Heating & Sheet Metal Inc at 605-342-5107 right away.

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 kick on if the switch was off. (Not sure where your furnace is? Look in your basement, garage or utility closet. It could also be placed in a crawl space or attic.)

Replace Your Air Filter

Dirty, closed off air filters often create issues 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 climb, because your furnace is starting up 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 locate your air filter inside your furnace’s blower component, attached filter case or wall-mounted return air grille. Its location depends upon what model of furnace you have.

Replace furnace filter

When switching out 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 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 once a 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 change 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 leaking water or there’s standing water in the pan.

  • If your pan has a PVC pipe/drain: Be 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 water in the pan, call us at 605-342-5107. You will likely need a new pump.

Peek Inside Your Furnace

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

Reach out to us at 605-342-5107 if you see anything other than a solid, colored light or blinking green light. Your furnace is likely giving an error code that demands professional assistance.

Clean Your Flame Sensor

Is your furnace making an effort to start but turning off without producing heat? A dirty flame sensor could be to blame. When this takes place, your furnace will try to switch 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.

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 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 updated. Or something else could be the problem. Call us at 605-342-5107 for help if this happens.

Relight the Pilot Light

If your furnace is an older model, its pilot light could be 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 bring the flame of a long lighter to the pilot light opening.
  • Stop holding the “reset” button once the pilot light is lit.

Contact us at 605-342-5107 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 turn on?

Call us today at 605-342-5107 or use our online scheduler. We’ll come out to your home and find out what’s wrong.

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