Continuous RED flash
Twinning error, incorrect 24V phasing, or no power to twinned unit
This code typically points to
- Improper twinning wiring
- 24V phasing mismatch between twinned units
- Loss of power to secondary twinned furnace
Next checks to confirm
- Verify twinning wiring against diagram
- Check 24V phasing on both units
- Verify power to secondary unit
Escalation
If twinning wiring and power are correct, board fault is possible.
Reset behavior
Clears when twinning issue is resolved.
Urgent
Fix now