furnace repair

Lexington is Getting Cold, but My Furnace Wont Turn On

Troubleshooting your furnace might feel like an intimidating task when your heat won’t work. But it doesn’t have to be like that.

There are a couple of fast, reasonable fixes you can do yourself to prevent a furnace repair call.

If your furnace won’t turn on, won’t stay on or won’t ignite, try the troubleshooting list below before calling an HVAC professional.

If you find you need help from an expert and live in Lexington, Kelley Mechanical can assist you. We work on most types of heating systems.

If it’s time for a new heating system, we also do furnace replacement in Lexington.

While you’re chatting with us, think over a regular furnace maintenance plan from Kelley Mechanical that might help you avoid breakdowns in the future. We can tell you how regularly your furnace should be examined by one of our NATE-certified professionals.

Use our easy guide below to start troubleshooting your furnace. Most of these steps don’t require mechanical know-how.

Steps for Furnace Troubleshooting

Check the Thermostat

To start, make sure your thermostat is instructing your furnace to turn on.

If you have a digital thermostat:

  • Replace the batteries if the screen is blank. If the digital screen is jumbled, the thermostat may need to be replaced.
  • Make sure the switch is set to “heat” rather than “off” or “cool.”
  • Ensure the program is showing the correct day and time and is set to “run.” If you’re having problems overriding the program, set the temperature by using the up/down arrows and press the “hold” button. This will make the furnace to turn on if thermostat programming is causing trouble.
  • Increase the temperature setting to 5 degrees warmer than the room temperature.
Digital Thermostat

If your furnace hasn’t started within few minutes, make sure it has power by toggling the fan switch from “auto” to “on.” If the fan doesn’t start, your furnace may not have power.

If you have a smart thermostat—like one made by Nest, Ecobee, Lux, Honeywell or Bosch—troubleshooting is very model-specific. Check the manufacturer’s website for help. If you still can’t get your Wi-Fi thermostat to work, contact us for assistance.

Lennox Smart Thermostat

Examine Breakers and Switches

Next, you will need to check if your breaker and furnace switch are on.

  • Look for your house’s main electrical panel. If you don’t know where it is, look for a gray metal box in your basement, garage or closet.
  • Make sure your hands and feet are dry before touching the panel or breakers.
  • Locate the breaker labeled “furnace” or “heat,” and make sure it’s switched “on.” If the breaker has tripped, it will be in the middle or “off” position.
  • Using one hand, firmly switch the breaker to the “on” position. If the breaker immediately trips and pops back to “off,” don’t try to reset it and contact a professional from Kelley Mechanical at 859-209-3003 right away.

Regardless of your furnace’s age or brand, it has at least one standard wall switch located on or close to it.

  • Make sure the switch is flipped up in the “on” position. If it was turned off, it could take your furnace up to five minutes to turn on. (If you don’t know where to find your furnace, look in your basement, garage or utility closet. It could also be in a crawl space or attic.)

Replace Your Furnace’s Air Filter

When it comes to furnace issues, a dirty, clogged air filter is regularly the top offender.

If your filter is too dirty:

  • Your furnace won’t stay on, or it could overheat from limited airflow.
  • Your energy bills could go up because your furnace is turning on more often.
  • Your furnace could fail prematurely because a dirty filter causes it to work harder.
  • Your furnace can lose power if an overly dirty filter causes the breaker to trip.

Depending on what model of furnace you own, your air filter is located inside the blower compartment of your furnace, an attached filter case or wall-mounted return air grille.

Replacing a furnace filter

To replace your filter:

  • Turn off your furnace.
  • Remove the filter and tilt it toward the light. If you can’t see light through it, get a new one.
  • Insert the new filter with the arrow pointing toward the furnace to avoid damage.

Flat filters should be replaced once a month, while pleated filters should last about three months. You can also use a washable filter that will last about 10 years. If you have children or pets, you may have to replace your filter more frequently.

To make the process smoother in the future, use a permanent marker on your furnace housing or ductwork to list the airflow direction and filter size.

Examine the Condensate Pan

Also known as drain pans, condensate pans catch water your furnace removes from the air.

If water is dripping out of your furnace or its pan has standing water in it, follow these steps.

  • If your pan has a drain (look for a PVC pipe), check that it isn’t clogged. If it needs to be drained, use a special pan-cleaning tablet you can get at home improvement or hardware stores.
  • If your pan has a pump, inspect the float switch. If the switch is stuck “up” with water in the pan, contact Kelley Mechanical at 859-209-3003, because you will possibly need a new pump.

Peek Inside Your Furnace

If malfunctions keep on happening, look inside your furnace’s plastic window to check the status of the blower motor. Depending on the model, the light could also be attached on the outside of your furnace.

If you see anything except a steady, colored light or blinking green light, call Kelley Mechanical at 859-209-3003. Your furnace may be emitting an error code that is calling for professional service.

Clean the Flame Sensor

If your furnace tries to start but shuts off without distributing heat, a dirty flame sensor could be responsible. When this happens, your furnace will try to turn on three times before a safety feature shuts it down for about an hour.

If you feel comfortable with opening up your furnace, cleaning your flame sensor is something you can do yourself. Or, one of our HVAC experts at Kelley Mechanical can do it for you.

If you want to clean the sensor yourself, you’ll need:

  • A 1/4” hex screwdriver or wrench
  • Piece of light grit sandpaper, steel wool or emery cloth
  • A dry, clean paper towel

Next:

  • Disable the furnace’s power by using its wall switch or breaker. If your gas valve is not electric, you will need to shut off the gas as well.
  • Take off the furnace’s front panel and trace the wire to the flame sensor.
  • Unscrew the rod and use your sandpaper, steel wool or emery cloth to gently rub the metal rod.
  • Wipe off the rod with a paper towel.
  • Remount the sensor.
  • Replace the furnace doors.
  • Turn the furnace’s power back on. It might proceed through a set of checks before resuming regular operation. If your furnace doesn’t ignite, the sensor may need to be replaced or something else might be wrong. If this happens, get in touch with Kelley Mechanical at 859-209-3003 for assistance.

Relight the Pilot Light

If you have an older furnace, the pilot light could be extinguished. To relight it, find the instructions on a label on your furnace, or follow these steps.

  • Locate the switch on the bottom of your furnace labeled “pilot,” “on” and “off.”
  • Turn the switch to the “off” position.
  • Wait at least five minutes to avoid possibly sparking a fire.
  • Turn the knob to “pilot.”
  • Press 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.

If you have followed the instructions twice and the pilot light still won’t light or stay lit, get in touch with Kelley Mechanical at 859-209-3003.

Check Your Fuel Source

Try turning on another gas appliance. If it doesn’t work, your natural gas service could be turned off, or you could be out of propane.

Kelley Mechanical Can Help with Furnace Problems

Followed our troubleshooting guide but your furnace still won’t work?

Call us today at 859-209-3003 or use our online scheduler. We’ll come out and figure out the problem.

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