9 FLASHES
Ruud
Reversed Line Polarity / Ground Fault
The status LED shows 9 flashes; the furnace may not respond to the thermostat, or the blower may run unexpectedly.
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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
Hot and neutral reversed at the service panel or furnace, a shared neutral with other circuits, a loose ground wire, or incorrect wiring of a new control board.
How to Fix / Troubleshooting
Safety: This is an electrical wiring issue. If you are not trained, contact an electrician or HVAC technician.
Steps to check:
- Inspect furnace junction box: With power off at the breaker, remove the furnace electrical cover. Verify black (hot) is on the L1 terminal, white (neutral) is on the neutral bar or N terminal, and the green/bare wire is on ground.
- Check breaker panel: Confirm the furnace circuit is wired correctly and not improperly sharing neutrals with other circuits.
- Verify board connections: If a control board was recently replaced, compare wiring to the Ruud's wiring diagram on the blower door. Correct any miswired connections.
- Test with outlet tester (if corded): Use a polarity tester to confirm correct hot/neutral/ground connections at the receptacle.
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Repair Difficulty
Hard
4/5
Required Part
Electrical Supply Wiring
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