3 red flashes
Pressure switch open when it should be closed
This code typically points to
- Faulty inducer
- Blocked vent pipe
- Broken pressure-switch hose
- Disconnected switch or inducer wires
- Faulty pressure switch
Next checks to confirm
- Verify inducer operation
- Inspect venting/intake and hose routing
- Use manometer to verify vent pressure (TM8Y)
Escalation
Repeated with verified draft pressure points to switch or control.
Reset behavior
If recurring during call, can advance to lockout logic.
Urgent
Fix now