e3.4
Open Pressure Switch, 2nd Stage (S8X2 2-stage only)
This code typically points to
- 2nd-stage pressure switch open
Next checks to confirm
- If PS2 does not close within 45 seconds, PS2-open error is declared and furnace operates in 1 stage
Escalation
Falls back to 1-stage heat
Reset behavior
Clears when PS2 proves closed correctly.
Urgent
Fix now