American Standard · Furnace / HVAC
3 flashes Pressure switch error
What this code means
The pressure switch isn't closing when the inducer motor starts (or it reopens mid-cycle), so the control won't allow gas to flow. This is the safety check confirming the inducer is actually pulling exhaust through the flue.
Most likely causes
- Blocked vent termination
- Failing inducer motor
- Condensate line blockage
What to try first
Check the exterior vent cap for blockage from debris, snow, or nests, and make sure the condensate line isn't clogged or frozen. Don't bypass the switch to force the furnace to run.
Safety note: if this code returns after one clean reset, stop resetting it — repeated lockouts usually mean a real fault that needs a licensed technician. Never bypass a safety switch.
FAQ
What does American Standard error code 3 flashes mean?
Pressure switch error. The pressure switch isn't closing when the inducer motor starts (or it reopens mid-cycle), so the control won't allow gas to flow. This is the safety check confirming the inducer is actually pulling exhaust through the flue.
Can I fix American Standard code 3 flashes myself?
Usually not. Check the exterior vent cap for blockage from debris, snow, or nests, and make sure the condensate line isn't clogged or frozen. Don't bypass the switch to force the furnace to run. If the code returns after one reset, it needs a licensed technician.
What causes American Standard code 3 flashes?
The most common causes are: blocked vent termination; failing inducer motor; condensate line blockage.
Other American Standard furnace codes
All American Standard furnace error codes →
Other furnace brands: Trane · Carrier · Lennox · Goodman · Amana · Rheem · Bryant · Generic · Nest
This information may contain errors or not apply to your exact model — always double-check it against your appliance's own manual before acting. If there's any chance of a gas, fire, electrical, carbon monoxide, or other safety hazard, stop and call a licensed professional or the appropriate agency (e.g. your gas utility) instead of relying on this page alone.