45
Day & Night Hard Lockout / Multiple Faults Detected

Furnace LED flashes code 45; furnace may shut down and require manual reset. Often indicates control board lockout due to repeated faults.

Advertisements

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.

Advertisements

Possible Causes

Repeated ignition failures, repeated limit trips, persistent pressure switch faults, control board internal error

How to Fix / Troubleshooting

Safety first: Do not repeatedly reset a furnace that is locking out without identifying the cause.

  • Record prior codes: Many Day & Night boards store the last few fault codes. Refer to the LED flash history (if available) to identify the underlying issue (e.g., 14, 33, 31).
  • Power cycle: Turn power OFF for at least 5 minutes to clear hard lockout, then ON. Observe the next fault code that appears during operation.
  • Address root cause: Use the specific fault code troubleshooting steps (ignition, limit, pressure) rather than only resetting.

If the furnace frequently enters hard lockout with varying codes, the control board or multiple components may be failing. Professional diagnosis is recommended.

Advertisements

Repair Difficulty

Hard 4/5

Required Part

Integrated Furnace Control Board
Check Price on Amazon

We may earn a commission from links on this page.

Advertisements