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Identifying a Control Board Failure

As the conductor of your HVAC system, the control board commands your system to function to work. If the board fails, your HVAC system won't be able to function, and you will experience issues such as poor airflow, inconsistent temperatures, or no warm or cold air at all.

Why Do Control Boards Fail?

Your HVAC system's control board relies on various electrical sources for power. So, if one of those power sources malfunctions, such as the wiring, it can fail. It can also fail if the control board itself is overworked and burns out.

How to check for a failed control board

  • When your HVAC system is running, listen closely. If you hear the fan cut short of its normal cycle, that’s an indicator of a control board issue in your home.

  • The control board receives commands from the thermostat to tell the system what heating or cooling process it should perform. Often, the control board can be found at the furnace and is located behind the lower door panel.

    warning

    CAUTION: Do not open the access panel unless you've already turned off the power.

  • Most control boards have warning lights to alert you when there's an issue. There is usually a small, clear viewing window where the diagnostic LED light can be seen. Different lights indicate different diagnostic issues.

    If you see a light on your control board, note the number of blinks before turning the power off to the furnace. Once power is turned off, the diagnostic code will be erased. Check the owner's manual or consult a technician to find out what's causing the indicator light to come on.

  • Turn off the power to the furnace and open the access door to take a closer look at the board. Look for black burn marks and wires that may be burnt or loose. If you see signs of damage, there may have been an electrical failure. A technician must be called in to determine what caused it. Be sure to tell them of any diagnostic codes that you observed.

    warning

    CAUTION: Always turn the power off to the furnace before removing any door panels.

  • If you don't see any outward signs of an issue, but still suspect it's your control board, you'll need to call a technician to run a diagnostic on it. A technician should check the function of individual components on the control board, including: - start the induced draft motor - see if the pressure switch closes - determine if the control ignites the pilot or if the hot surface ignitor glows a bright orange color - the timer should then open the gas valve, light the burners, which must be confirmed by the flame sensor - the furnace blower should start - once the thermostat has reached its setpoint, the control should shut off the gas - the inducer should run for a short period to purge the venting pipes - the furnace fan should be turned off by a timer allowing the remaining heat to be given up to the conditioned space

    If any of these components aren't working, the control board is likely bad.

    warning

    CAUTION: These component checks should be performed by a trained technician.

What To Do If Your Control Board Has Failed

If your control board has failed, you'll need to locate and fix any issues with the electrical systems powering it, such as by rewiring your system or restoring power to the unit.

If the electrical issue is beyond your realm of DIY expertise, or you can't locate the issue at all, you will require expert service.

Want to fix a control board failure?

NOTE: This content is for informational purposes only, and HomeX and its affiliates disclaim all liability related to it. If you decide to perform any tasks based on this information, you assume all risks, including the risk of loss or damage to property or personal injury.

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