CODE 45
Fraser-Johnston
Control Board Lockout Due to Multiple Faults
LED flashes four short and five long blinks; furnace locked out; no heating cycles.
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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 trips, Internal IFC fault, Incorrect line voltage
How to Fix / Troubleshooting
Safety first: Turn off power and gas before extended troubleshooting.
- Record prior codes: Many Fraser‑Johnston boards store the last few fault codes. Refer to the diagnostic label to interpret them and address root causes (ignition, limit, pressure, etc.).
- Reset lockout: Turn off power for at least 5 minutes, then restore. Observe startup sequence and note any new codes.
- Check line voltage: Verify that supply voltage is within the range specified on the furnace nameplate (typically 115–125 VAC). Low or high voltage can cause control issues.
- Professional service: If lockout recurs after addressing obvious issues, the IFC board may need replacement and the entire system should be evaluated by a technician.
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Repair Difficulty
Professional Required
5/5
Required Part
Integrated Furnace Control Board
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