8 Reasons a Furnace Will Not Work

By | June 17, 2022

8 Reason a Furnace Will Not Work Fall and Winter Maintenance Tips
If your furnace is giving you trouble and not starting, you can try several things before calling a technician.

While the furnace may have a problem that requires a technician to troubleshoot, there are often simple causes.

Below are eight common reasons a furnace will not start to try out before calling a professional.

Of course, if in doubt, be sure to call a certified tech.

8 Reasons a Furnace Will Not Work

  1. Check the Thermostat Settings
  2. 8 Reason a Furnace Will Not Work Fall and Winter Maintenance Tips Thermostat
    Be sure the thermostat is set for heat and the temperature is set high enough for the furnace to start.

    This may seem obvious, but it happens all the time.

  3. Check the Thermostat Batteries
  4. furnace thermostat batteries
    It is easy to forget that a thermostat needs batteries to run and needs replacing roughly once a year.

    Simply replace them with new ones to rule out bad batteries as the cause.

  5. Replace the Furnace Filter
  6. Replace the furnace filter
    Most people are aware that the furnace filter needs to be replaced when it gets dirty.

    What they may not know is a dirty air filter can cause no airflow through a furnace, causing it to shut down.

    If a furnace becomes too hot, a safety switch will turn it off.

    How often the air filter needs to be replaced depends on where you live. For example, in desert areas, dust will clog filters faster compared to other places.

  7. Be Sure the Gas Valve is Turned To On
  8. Furnace gas valve on

    If you have recently moved into a home or live with someone else that may have had access to the furnace, check and be sure the gas valve is turned ON.

    Many times people turn it to off when the summer comes around when the furnace is not needed.

  9. Be Sure the Power is On
  10. power off the furnace
    If the furnace doesn’t turn on at all, besides making sure the thermostat is set correctly, check that the power is turned on.

    This is usually done with a switch but can be a breaker or someone simply unplugged it.

  11. Check the Door for a Safety Switch.
  12. furnace panel door switch
    Many furnaces have a safety switch that will turn the furnace off when the panel door is taken off.

    If someone recently has opened the panel door, it sometimes needs a tap near the switch to close.

  13. Check the Pilot Light or Igniter
  14. Furnace pilot light
    Most modern furnaces will have an igniter that comes on and glows to light a flame, but many furnaces also use a pilot light, where a small flame is used to light the furnace.

    If you have an igniter, it should glow red hot so that it can start a flame when the gas comes on.

    A pilot light may stay on all the time or may only come on when needed depending on your furnace. Some pilot lights that stay on constantly have a sequence of events that need to be done for it to light and stay on. Other furnaces use a spark that will light the pilot light only when needed.

    Check the door panel and inside of the furnace for what type you have. If you can’t find any information on the panel then you can always Google your furnace name and model number to find out how the flame is lit.

  15. Check for Blocked Vents
  16. Furniture or other items such as clothes can block air from flowing through the vents into a home.

    Check the vents and be sure that any recently moved furniture or anything else is not blocking the vents from blowing warm air in. If only one vent is blocked, it usually only will affect that room, but if many vents are blocked, then it can affect the entire home.

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