Furnace will not run; LED shows 9 flashes; blower may run at low speed.
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.
Possible Causes
How to Fix / Troubleshooting
Safety: This involves line-voltage diagnostics. If you are not experienced, contact a licensed electrician or HVAC technician.
Steps:
- Test receptacle or junction box: Use a receptacle tester or multimeter to verify correct hot, neutral, and ground orientation at the furnace power source.
- Inspect wiring connections: With power off at the breaker, open the furnace junction box and confirm the black (hot) wire is connected to L1, white (neutral) to neutral, and green/bare to ground.
- Check ground bond: Ensure the ground wire is securely attached to the furnace cabinet and that the cabinet is not isolated by paint or corrosion.
- Reset control board: After correcting polarity/ground, restore power and observe if the 9-flash code clears.
If polarity and grounding are correct and the code remains, the control board's sensing circuit may be faulty and require replacement.
Repair Difficulty
Required Part
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