Goodman GMSS920803BN Error Code 3 Flashes: Pressure Switch Stuck Open
What Does Code 3 Flashes Mean?
Three flashes on the Goodman GMSS920803BN diagnostic LED indicate that the pressure switch circuit is not closed. The inducer motor is running, but the pressure switch has not detected sufficient draft to allow ignition. This is a safety feature that prevents the burners from firing if exhaust gases cannot be properly vented.
The inducer motor creates a vacuum through the heat exchanger and vent pipe. The pressure switch senses this vacuum and closes to signal the control board that venting is safe. When the switch fails to close, the inducer continues running but the furnace will not proceed to ignition.
For a 92% efficiency furnace like the GMSS920803BN, one of the most common causes is a blocked condensate drain. High-efficiency furnaces produce condensation during operation, and if the drain trap or line is clogged, water backs up into the inducer housing and blocks airflow. Other common causes include a blocked exhaust or intake pipe, a kinked or disconnected pressure switch hose, a weak inducer motor, or a faulty pressure switch.
Common Causes
When to Call a Professional
Contact a licensed HVAC technician if:
- The code persists after clearing the condensate drain and checking the vents
- The inducer motor sounds weak, rattles excessively, or does not spin
- Water keeps backing up into the inducer housing despite clearing the drain
- The pressure switch hose is connected and clear but the switch will not close
- You are unable to access or identify the condensate drain components
✓ Verified against manufacturer service manual — March 2026