5 FLASH
Fraser-Johnston
Flame Sensed With Gas Valve Off (False Flame) or Rollout/Open Safety
Furnace does not respond to thermostat; LED flashes five times repeatedly; no inducer or blower operation.
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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
Shorted or contaminated flame sensor, Flame rollout switch tripped, Shorted wiring to flame sensor terminal, Defective integrated furnace control (IFC) board
How to Fix / Troubleshooting
Safety first: If you see signs of flame rollout (scorch marks, melted wiring, burning smell), shut off gas and power immediately and call a licensed HVAC technician. Do not attempt to operate the furnace.
- Inspect flame rollout switches: With power off, locate the manual reset rollout switches near the burner compartment. If a rollout switch has a small red reset button, press it gently until it clicks. If it trips again, stop and call a professional—this indicates a serious combustion problem.
- Check flame sensor: Remove and clean the flame sensor rod with fine steel wool. Oil or soot can cause false readings. Reinstall and ensure the wire is secure and not shorted to ground.
- Inspect wiring harness: Look for damaged insulation or wires touching the burner or metal surfaces, especially the wire from the flame sensor to the IFC board.
- Reset control: Turn off power for 30 seconds, then restore. If the 5‑flash code returns without a call for heat, the IFC board may be defective and should be replaced by a technician.
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Repair Difficulty
Professional Required
5/5
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