Error code reference
Trane Furnace Error Code 3 Flash
Pressure switch or inducer error
Pressure switch or inducer error – a pressure switch is either opened or closed contrary to normal operating sequence.
First step from the service manual
Verify all wiring and pressure switch tubing is correct per diagrams; cycle power to furnace, set comfort control to heat, and raise set-point 5 degrees above actual room temperature.
The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.
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- Step-by-step tests with expected resistance, voltage, and continuity values
- Wiring diagram references and connector pinouts from the OEM service manual
- Verified part numbers when replacement is required
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