Goodman GMSS960803BN Error Code 3 Flashes: Pressure Switch Stuck Open
What Does Code 3 Flashes Mean?
Three flashes on the GMSS960803BN's Integrated Control Module indicate the pressure switch circuit did not close. The inducer motor runs continuously trying to establish draft, but the switch never senses enough vacuum to close its contacts, so the board holds off ignition. This is a venting-safety interlock: the furnace refuses to light the burners until it can confirm exhaust is being drawn safely.
The GMSS960803BN is a 96% AFUE condensing furnace, and that design shapes the likely causes. A high-efficiency furnace extracts so much heat that its exhaust cools and forms liquid condensate in a secondary heat exchanger, which must drain away continuously. If the condensate trap or drain line clogs, water backs up into the inducer or drain path and the switch cannot close. The sealed PVC intake and exhaust pipes add more failure points than an old atmospheric furnace: a blocked or iced-over termination, an obstructed intake, or a disconnected, pinched, or water-filled pressure-switch hose all keep the switch open. A weak inducer or an out-of-spec switch can do the same.
This is the mirror image of the 2-flash "pressure switch stuck closed" code. Two flashes means the switch reads closed before the inducer even starts; three flashes means the inducer is running yet the switch will not close. Because clearing it can involve the flue and combustion venting, and because a misdiagnosis leaves a furnace unable to prove safe exhaust, Goodman treats this as a professional diagnosis.
What You'll Notice
- The inducer motor runs and keeps running, but the burners never light
- The furnace cycles the inducer on a heat call yet no warm air follows
- The diagnostic LED blinks three times, pauses, and repeats
- Possible gurgling or standing water near the condensate trap on a high-efficiency unit
- In cold weather, visible ice or frost on the outdoor PVC vent termination
Common Causes
How This Is Diagnosed
A technician follows the draft path the switch is monitoring. They confirm the inducer is actually spinning at speed, then check the pressure-switch hose for kinks, cracks, disconnection, or trapped water. Next the condensate trap and drain line are checked for the blockage that is common on 96% furnaces, and the PVC intake and exhaust are inspected end to end — proper length, elbows, and a clear outdoor termination free of ice, nests, or debris. Only after the venting and drain are proven clear is the pressure switch itself tested against its rated setpoint or the inducer evaluated for weak output. The venting and combustion-side checks are why this is technician work rather than a homeowner fix.
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 furnace never ignites
- Water is backing up at the condensate trap or the drain line appears clogged
- The outdoor PVC vent or intake termination is blocked, iced over, or nested in
- The pressure-switch hose looks connected and clear but the switch still will not close
- The inducer sounds weak, rattles, or does not reach full speed
Frequently Asked Questions
Why does my high-efficiency Goodman furnace keep throwing a 3-flash pressure switch code?
On a 96% condensing furnace like the GMSS960803BN, a clogged condensate drain is one of the most common reasons the pressure switch cannot close, along with a blocked PVC vent or a kinked switch hose. A technician should trace the drain and venting to find the blockage.
Could a blocked outdoor vent cause the 3-flash code?
Yes. Snow, ice, leaves, or a bird or insect nest at the PVC exhaust or intake termination restricts draft so the pressure switch never senses enough vacuum to close. Clearing outdoor terminations and confirming safe venting is part of a professional diagnosis.
Is 3 flashes the same as the pressure switch being stuck closed?
No. Three flashes is the switch stuck open — the inducer runs but the switch never closes. Two flashes is the opposite, the switch reading closed before the inducer starts. Same component, opposite conditions.
How often do condensate drains clog on furnaces like this?
It varies by installation and water quality, but condensate blockages are a routine maintenance item on high-efficiency furnaces and tend to show up more as a unit ages. Annual service that includes flushing the drain reduces how often it happens.
✓ Verified against manufacturer service manual — March 2026