9 FLASH
Fraser-Johnston
Line Voltage Polarity or Ground Fault
Furnace will not start; LED flashes nine times repeatedly; no inducer or blower response to thermostat.
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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
Reversed hot/neutral at furnace power connection, Missing equipment ground, Shared neutral or miswired service switch, Defective integrated furnace control (IFC) board ground sensing
How to Fix / Troubleshooting
Safety first: This involves 120 VAC line voltage. If you are not experienced with electrical work, contact a licensed electrician or HVAC technician.
- Check service switch and outlet: If the furnace is plugged into a receptacle, use a plug‑in outlet tester to verify correct hot/neutral/ground. If hard‑wired, turn off the breaker and verify wiring at the junction box matches the wiring diagram (hot to L1, neutral to neutral, ground to chassis).
- Inspect ground connection: Ensure the green or bare copper ground wire is securely attached to the furnace cabinet ground screw.
- Reset control: After correcting wiring, restore power and observe the LED. If the 9‑flash code persists, the IFC board may be damaged and require replacement.
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Repair Difficulty
Professional Required
5/5
Required Part
Integrated Furnace Control Board
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