furnace repair

What to do When Your Furnace Wont Start

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

You might 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 quick and inexpensive (or even free).

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

When you have to have a pro in Buellton, Allstar Heating & Air Conditioning can help.

We repair and maintain 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 neglected routine maintenance. These evaluations often reveal an expensive problem before it gets worse—and causes your HVAC system to break down.

During your appointment, our NATE-certified professionals will carefully inspect your furnace, make sure it’s operating properly and lubricate moving parts. A well-maintained furnace often lasts longer and operates more efficiently, saving you more on your heating bill.

Ready to begin 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:

  • Switch out the batteries if the screen is off. If the digital screen is scrambled, you may need a different thermostat.
  • See if that the switch is set to “heat” instead of “off” or “cool.”
  • Find out if the program is displaying the right day and time and is set to “run.” If you can’t change the program, fix the temperature with the up/down arrows and press the “hold” button. This will compel the furnace to turn on if thermostat programming is causing complications.
  • Set the temperature to 5 degrees warmer than the room’s temperature.
Digital Thermostat

Your furnace should kick on 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 work instantly, your furnace may not have 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 turn on, call us at 805-242-9638 for help.

Smart Thermostat

Check Breakers and Switches

After that, 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 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 Allstar Heating & Air Conditioning at 805-242-9638 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 start if the switch was off. (Not sure where your furnace is located? Look in your basement, garage or utility closet. It could also be located 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 turn off too soon, due to dust in the filter diminishing 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 excessively dirty filter can cue 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 changing out your filter:

  • Shut down your furnace completely.
  • Grab the filter, hold it up to the light and look through it. Get a new filter if you can’t see light through it.
  • Replace the new filter with the arrow pointing toward the furnace to avoid damaging your system.

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 typically 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 replace your filter on a more regular basis.

Inspect Your Condensate Pan

Condensate pans, or drain pans, catch water your furnace pulls 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: Make 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 805-242-9638. You will most likely need a more modern pump.

Look 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 placed on the outside of your furnace.

Reach out to us at 805-242-9638 if you see anything other than a solid, colored light or blinking green light. Your furnace is likely giving an error code that needs professional help.

Clean Your Flame Sensor

Is your furnace attempting to start but shutting down without generating heat? A dirty flame sensor could be at fault. When this takes place, 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 alright opening up your furnace. We can also do it for you.

Ready 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 shut off the power. Shut off the gas too if your gas valve is not electric.
  • Remove 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.
  • Replace 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 wrong. Call us at 805-242-9638 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 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.
  • Turn 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 805-242-9638 if you’ve followed the guide twice and the pilot won’t light or stay lit.

Check Your Fuel Source

Are other gas appliances working? 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 805-242-9638 or use our online scheduler. We’ll come out to your home and identify what’s wrong.

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