furnace repair

What to do When Your Furnace Will Not Turn On

It might seem 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 most of these fixes are brief and low-cost (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 need a pro in Lodi, Tokay Heating and Air Conditioning can help.

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 usually caused by a lack of routine maintenance. These evaluations often disclose a high-cost problem before it gets worse—and causes your HVAC system to fail.

During this service, our NATE-certified professionals will carefully inspect your furnace, make sure it’s functioning 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 tackle troubleshooting your furnace? Follow our step-by-step guide below.

Steps for Troubleshooting Your Furnace

Check Your Thermostat

Start by looking at your thermostat. Is it telling your furnace to turn 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 a new thermostat.
  • Confirm that the switch is set to “heat” instead of “off” or “cool.”
  • Make sure 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 pushing the up/down arrows and press the “hold” button. This will require the furnace to turn on if thermostat programming is causing an issue.
  • Set the temperature to 5 degrees warmer than the room’s temperature.
Digital Thermostat

Your furnace should turn on fairly quickly. If it doesn’t, make sure it has power by sliding the fan switch from “auto” to “on.” If the fan doesn’t run 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—refer to the manufacturer’s website for help. If you can’t get your smart thermostat to work, call us at 209-257-3156 for assistance.

Smart Thermostat

Check Breakers and Switches

After that, you will have 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.
  • Locate 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 midpoint or “off” position.
  • With one hand, firmly push 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 Tokay Heating and Air Conditioning at 209-257-3156 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 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, closed off air filters often create problems that are easily avoidable.

  • Your furnace can overheat and stop working 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 cue the breaker to trip.

You can get to your air filter inside your furnace’s blower component, attached filter case or wall-mounted return air grille. Its placement depends upon what kind of furnace you have.

Replace furnace filter

When switching 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.
  • Put in the new filter with the arrow pointing toward the furnace to avoid damaging your system.

To make the process simpler next time, use a permanent marker on your furnace housing or ductwork to indicate the airflow direction and filter size.

We recommend replacing flat filters monthly. Pleated filters generally last about three months. You can also get a washable filter that will be good for 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, 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: Check 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: Check out the float switch. If the switch is “up” and there’s water in the pan, call us at 209-257-3156. You will most likely need a new pump.

Look Inside Your Furnace

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

Reach out to us at 209-257-3156 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 attempting to start but shutting off without producing heat? A soiled flame sensor could be to blame. When this occurs, 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.

Want 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 also if your gas valve is not electric.
  • Remove your furnace’s front panel and track 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 turn on, the sensor might need to be switched out for a new one. Or something else could be wrong. Call us at 209-257-3156 for guidance if this happens.

Relight the Pilot Light

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

Contact us at 209-257-3156 if you’ve followed the steps 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 turn on?

Call us today at 209-257-3156 or use our online scheduler. We’ll come out to your home and figure out what’s wrong.

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