25
Model selection or setup error
This code typically points to
- Missing/incorrect model plug
- SW1-1 or SW1-6 improper position
- Thermostat call with setup switch on
- Mismatched twinned furnaces
- Incompatible 58UVB model-plug recognition on older board date codes
Next checks to confirm
- Verify model plug
- Verify setup-switch position
- Verify no call is present during setup functions
Escalation
If plug/switching are correct and fault persists, control replacement becomes more likely.
Reset behavior
If flashes only four times at power-up, board is defaulting to stored model selection; persistent flashing indicates active setup fault.
Urgent
Fix now