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 has not closed even though the induced-draft blower is running. The inducer pulls a vacuum through the heat exchanger and vent system, and the pressure switch must sense that vacuum and close to prove venting is safe before the board will light the burners. When the switch stays open, the inducer keeps running but the furnace cannot proceed to ignition.

The GMSS920803BN is a high-efficiency, 92%-class furnace that vents through sealed PVC piping and produces acidic condensate during normal operation. That design makes certain causes especially common: a condensate drain trap or line that has clogged and backed water up into the inducer housing, a blocked or improperly terminated flue or intake pipe, or a pressure switch hose that is pinched, disconnected, or filled with water. A weak inducer motor, an incorrect switch setpoint, or loose wiring can also keep the switch from closing.

This is the opposite of the neighboring 2-flash condition on the same board. Two flashes means the switch is already closed before the inducer starts (stuck closed), while three flashes means the switch fails to close after the inducer starts. The distinction guides the whole diagnosis: a 3-flash fault sends attention to draft and venting, not to a stuck switch.

What You'll Notice

• The inducer blower runs continuously but the burners never light and no heat is produced
• The LED repeats a three-flash pattern while the inducer keeps spinning
• You may see or hear water pooling near the furnace or in the condensate drain area
• In cold or windy weather the exhaust or intake pipe termination outside may be iced or blocked
• The furnace may start normally sometimes and fail other times if a drain or vent is partially restricted

Common Causes

How This Is Diagnosed

Because the inducer is confirmed running, diagnosis focuses on why the draft proof never reaches the switch. A technician checks the venting path first — the PVC flue and intake terminations outside for ice, nests, or debris, and the condensate drain trap and line for a clog that can back water into the inducer and choke airflow, which is a frequent cause on this high-efficiency model. The small pressure switch hose is inspected for kinks, disconnection, or trapped water.

If the venting, drain, and hose are all clear, the technician measures the vacuum the inducer actually produces and compares it to the switch's closing setpoint, since a weak inducer or a switch that no longer closes at spec will also throw this code. Confirming and clearing a blocked vent or drain can involve working on the sealed combustion system, so it is handled as service work rather than a homeowner repair on this furnace.

When to Call a Professional

This code involves components that are not homeowner-serviceable, so have a licensed HVAC technician diagnose and repair it. Keep in mind:

• The inducer runs continuously but the burners never light and the LED shows three flashes
• Water is backing up around the furnace or the condensate drain appears clogged
• The exhaust or intake pipe outside is blocked and you cannot safely clear it
• The vent, drain, and pressure switch hose look clear but the switch still will not close
• The inducer sounds weak, rattly, or slow to spin up

✓ Verified against manufacturer service manual — March 2026