What It Means
Pressure switch circuit failed to close or reopen properly.
Trane Furnace
Trane Furnace Error Code 3 Flashes
Troubleshooting guide for the Trane Furnace system fault 3 Flashes.
Possible Causes
- Blocked vent or exhaust pipe.
- Failed or non-starting inducer fan.
- Clogged condensate drain.
- Defective pressure switch.
Not sure which one it is — or if it's none of these? Try ACLogics today.
Disclaimer: This information is for general reference. Error codes can vary by model and production year. Always refer to your machine's specific manual and the information printed on the unit itself.
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Full Diagnosis
Pressure switch failure (venting/inducer problem). The pressure switch did not close or reopen appropriately.
All Recorded Causes
Inspect the vent/exhaust pipe for blockages (e.g. ice, debris) and ensure the inducer fan starts. Clean out condensate if applicable. Replace the pressure switch if it’s defective.
Verify Before Replacing Parts
- Confirm the exact Trane model family and furnaces context before acting on a generic code description.
- Walk the entire heating sequence in order instead of jumping straight to the reported code, watching for inspect the vent/exhaust pipe for blockages (e.g.
- Verify each safety device and prove where the sequence stops under live operation, including whether ice, debris) and ensure the inducer fan starts.
- After the correction, run the system long enough to confirm the furnaces fault does not return under normal load.
Still unsure about this fault?
ACLogics walks you through Trane Furnace diagnostics step-by-step — so you confirm the cause before swapping parts.
