45
Comfortmaker Control Board Lockout / Multiple Faults Detected

LED flashes code 45; furnace may lock out after multiple failed attempts.

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Repeated ignition failures, Repeated limit or rollout trips, Internal Comfortmaker control board fault, Unresolved underlying safety issue

How to Fix / Troubleshooting

Safety: A lockout indicates repeated unsafe or failed operation. Do not repeatedly reset without finding the cause.

Steps:

  • Power reset: Turn off power to the furnace for at least 30 seconds, then restore. Note any new error code that appears after the next attempt.
  • Review history: Many Comfortmaker boards flash the last fault code before lockout. Observe the LED pattern carefully and refer to the code list.
  • Address root cause: If the previous code was ignition-related (14, 34), focus on ignitor/flame sensor. If it was limit-related (33, 13), focus on airflow and overheating.
  • Do not bypass safeties: Never jump out limit switches, pressure switches, or rollout switches to keep the furnace running.

When to call a technician: If lockout recurs after basic checks, a professional should perform a full diagnostic to identify and correct the underlying issue.

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Repair Difficulty

Hard 4/5

Required Part

Furnace Control Board
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