9 red flashes
Reversed line polarity, grounding problem, or reversed low-voltage transformer wires
This code typically points to
- Incoming power polarity error
- Poor ground
- Transformer lead reversal
Next checks to confirm
- Verify line polarity with meter
- Verify furnace grounding path
- Inspect flame probe to chassis short
Escalation
Ignition sequence inhibited until corrected.
Reset behavior
Clears when corrected.
Service Soon
Schedule repair