Green FLASH / Red ON
Pressure switch open fault (does not close during inducer run)
This code typically points to
- Blocked vent or intake
- Inducer not creating sufficient draft
- Split or pinched pressure tubing
- Condensate/drain restriction on condensing furnaces
- Failed pressure switch
Next checks to confirm
- Verify inducer operation and actual draft
- Inspect pressure tubing/ports and condensate path
- Verify actual pressure-switch closure under call
Escalation
If inducer draft and venting prove normal but switch never closes, switch or board input is likely.
Reset behavior
Clears when proof is restored; repeated ignition failures can escalate into 1-hour lockout.
Urgent
Fix now