When your furnace won’t start, doing your own furnace repair in Manassas, Virginia, can feel pretty overwhelming.

Figuring out a furnace-related problem might feel like an overwhelming process when your heat won’t start. But it doesn’t have to be like that.

There are a few time-saving, low-cost 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 getting in touch with an HVAC professional.

If you find you need help from a heating and cooling professional and live in Manassas, Air-Right Energy Design can help you. We can repair most makes of heating systems and also provide emergency furnace repair.

If it’s time for a new heating system, we also offer furnace installation.

While you’re chatting with us, think over an annual furnace maintenance plan that may help you avoid breakdowns in the future. We can tell you how regularly your furnace should be checked by one of our NATE-certified professionals.

Go through our easy guide below to get started on troubleshooting your furnace. Most of these steps don’t require mechanical know-how.

Furnace Repair Checklist

1. Check the Thermostat

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

Digital Thermostat

Change 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 appropriate day and time and is set to “run.” If you’re having a hard time overriding the program, set the temperature by using the up/down arrows and press the “hold” button. This will cause the furnace to start if thermostat programming is causing trouble.

Increase the temperature setting to 5 degrees warmer than the room temperature.

If your furnace hasn’t kicked on within a couple minutes, make sure it has power by toggling the fan switch from “auto” to “on.” If the fan doesn’t begin to run, your furnace may not have power.

Smart Thermostat

If you have a smart thermostat—like one made by Nest, Ecobee, Lux, Honeywell or Bosch—troubleshooting is very model-specific. Take a look at the manufacturer’s website for help. If you still can’t get your Wi-Fi thermostat to work, call us at 703-260-1148 for heating and cooling service.

2. Examine Breakers and Switches

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

Find your house’s main electrical panel. If you have no idea where it is, search 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,” leave it alone and call a professional from Air-Right Energy Design at 703-260-1148 right away.

It doesn’t matter how old your furnace is or what brand it is, it has at least one standard wall switch located on or near 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 ignite. (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.)

3. Replace the Air Filter

When it comes to furnace issues, a grungy, clogged air filter is frequently to blame.

If your filter is too dirty:

  • Your furnace won’t keep heating your home, or it could overheat from reduced airflow.
  • Your energy bills could increase because your furnace is turning on more often.
  • Your furnace could break down prematurely because a dirty filter causes it to overwork.
  • Your furnace can lose power if an overly dirty filter causes the breaker to trip.

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

To replace your filter:

  1. Turn off your furnace.
  2. Remove the filter and hold it up to the light. If you can’t see light through it, use a new one.
  3. Put in the new filter with the arrow pointing toward the furnace to avoid damage.

Flat filters should be replaced monthly, while pleated filters should last about three months. You can also get a washable filter that will last about 10 years. If you have children or pets, you may have to put in a new filter sooner.

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

4. Inspect 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’s clear. If it needs to be drained, use a special pan-cleaning tablet you can buy at home improvement or hardware stores.
  • If your pan has a pump, take a look at the float switch. If the switch is stuck “up” with water in the pan, contact us at 703-260-1148, because you will possibly need a new pump.

5. Check for Furnace Error Codes

If malfunctions persist, look inside your furnace’s plastic window to verify the status of the blower motor. Depending on the model, the light could also be fixed on the outside of your furnace.

If you see anything other than a steady, colored light or blinking green light, call us at 703-260-1148 for HVAC service. Your furnace may be emitting an error code that requires professional assistance.

6. Clean the Flame Sensor

If your furnace tries to start but switches off without distributing heat, a dirty flame sensor could be at fault. When this occurs, your furnace will attempt 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 by yourself. Or, one of our heating service professionals 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:

  • Turn off 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.
  • Remove the furnace’s front panel and track 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 may go through a series of checks before continuing normal operation. If your furnace doesn’t start, the sensor may need to be replaced or something else may be wrong. If this happens, get in touch with us at 703-260-1148 for heating and cooling repair assistance.

7. Relight the Pilot Light

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

  • Look for 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 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.

If you have followed the instructions twice and the pilot light still won’t light or stay lit, call us at 703-260-1148 for furnace service.

Check Your Fuel Source

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

We Can Help with HVAC Repair

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

Call us today at 703-260-1148 or contact us online. We’ll come out and figure out the problem.

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