furnace repair

What to do When Your Furnace Will Not Start

It might feel stressful to troubleshoot your furnace when your heat won’t work. But it doesn’t have to be that way.

You may be able to bypass a furnace repair call with our DIY troubleshooting guide. You don’t need any technical skills. And many of these fixes are fast and affordable (or even free).

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

When you require a pro in West Columbia, Tri City Fuel & Heating Co., Inc. can lend a hand.

We work on 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 forgotten routine maintenance. These checkups often disclose a high-cost 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-kept 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 looking at your thermostat. Is it telling your furnace to switch on?

If you have a digital thermostat:

  • Change 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.”
  • Find out if the program is showing the correct day and time and is set to “run.” If you can’t override the program, change the temperature with the up/down arrows and press the “hold” button. This will compel the furnace to switch on if thermostat programming is causing complications.
  • Set the temp to 5 degrees warmer than the room’s temperature.
Digital Thermostat

Your furnace should start fairly quickly. If it doesn’t, double check that it has power by pushing the fan switch from “auto” to “on.” If the fan doesn’t work instantly, your furnace may not have power.

If you’re using 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 803-265-4208 for assistance.

Smart Thermostat

Check Breakers and Switches

After that, 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 touching 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 middle or “off” position.
  • With one hand, firmly move the breaker to the “on” position. If the breaker trips and goes back to “off” after you do this, leave it alone. Contact a professional from Tri City Fuel & Heating Co., Inc. at 803-265-4208 right away.

Your furnace has at least one wall switch placed 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 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 shut down too soon, due to dust in the filter hampering airflow.
  • Your energy bills could climb, because your furnace is turning on more often.
  • Your furnace may have a shorter life span, because it has to work harder.
  • Your furnace could lose power, because an extra 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 placement depends upon what type of furnace you have.

Replace furnace filter

When changing out your filter:

  • Shut down your furnace completely.
  • Grab 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 less difficult for yourself, 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 usually 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 switch out your filter more frequently.

Look at Your Condensate Pan

Condensate pans, or drain pans, catch water your furnace removes 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: Make 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: Find the float switch. If the switch is “up” and there’s fluid in the pan, call us at 803-265-4208. You will likely need a new pump.

Peek Inside Your Furnace

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

Contact us at 803-265-4208 if you see anything other than a stable, colored light or blinking green light. Your furnace is probably giving an error code that needs professional help.

Clean Your Flame Sensor

Is your furnace making an effort to start but shutting down without blowing heat? A filthy flame sensor could be to blame. When this happens, 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 tackle 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 shut off the power. Shut off the gas too 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.
  • 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 as usual. If it doesn’t start, the sensor might need to be replaced. Or something else could be the issue. Call us at 803-265-4208 for assistance if this happens.

Relight the Pilot Light

If your furnace is an older design, its pilot light could be out. 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.

Call us at 803-265-4208 if you’ve followed the guide 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 work?

Call us today at 803-265-4208 or use our online scheduler. We’ll come out to your home and figure out what’s wrong.

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