furnace repair

What to do When Your Furnace Refuses to Switch On

It might appear scary to troubleshoot your furnace when your heat won’t run. But it doesn’t have to be that way.

You may 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 fast 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 require a pro in Kingsville, Four Seasons Air Conditioning and Heating LLC can lend a hand.

We work on 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 generally caused by forgotten routine maintenance. These service appointments often disclose an expensive problem before it begins—and causes your HVAC system to fail.

During our visit, 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 charges.

Ready to start troubleshooting your furnace? Follow our step-by-step guide below.

Steps for Troubleshooting Your Furnace

Take a Look at Your Thermostat

Start by examining your thermostat. Is it telling your furnace to turn on?

If you have a digital thermostat:

  • Change the batteries if the screen is unresponsive. If the digital screen is scrambled, you may need a different 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, fix the temperature by using the up/down arrows and press the “hold” button. This will compel the furnace to switch on if thermostat programming is causing a problem.
  • Set the temperature 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 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—check the manufacturer’s website for help. If you can’t get your smart thermostat to turn on, call us at 361-214-1203 for support.

Smart Thermostat

Check Breakers and Switches

If you’ve already checked your thermostat, you will have 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 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 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 an expert from Four Seasons Air Conditioning and Heating LLC at 361-214-1203 as soon as possible.

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

Replace Your Air Filter

Dirty, clogged air filters often generate problems that are easily avoidable.

  • Your furnace can overheat and stop working too soon, due to dust in the filter diminishing airflow.
  • Your energy bills could increase, because your furnace is starting up more often.
  • Your furnace may fail permantly faster, because it has to work harder.
  • Your furnace could lose power, because a very dirty filter can cue 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:

  • Turn 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.
  • Install 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 recommend replacing flat filters each month. 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 replace your filter more frequently.

Look at Your Condensate Pan

Condensate pans, or drain pans, capture 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: Check 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 361-214-1203. You will likely need an updated pump.

Peek Inside Your Furnace

You can check the condition of your furnace’s blower motor by peeking inside the plastic window. Depending on the kind, this light could be somewhere on the outside of your furnace.

Contact us at 361-214-1203 if you see anything other than a solid, colored light or blinking green light. Your furnace is probably giving an error code that needs professional service.

Clean Your Flame Sensor

Is your furnace making an effort to start but shutting down without producing heat? A dirty flame sensor could be at fault. 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 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 shut off the power. Shut off the gas too 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 normally. If it doesn’t turn on, the sensor might need to be replaced. Or something else could be the issue. Call us at 361-214-1203 for help 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.
  • Switch 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 361-214-1203 if you’ve followed the instructions 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 361-214-1203 or use our online scheduler. We’ll come out to your home and identify what’s wrong.

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