Trane Furnace Pressure Switch Fault — 3-Flash Code Diagnosis and Repair
A 3-flash fault code on a Trane furnace indicates a pressure switch fault — specifically, the pressure switch failed to close (or opened unexpectedly) during a heating cycle. This is one of the most common Trane furnace fault codes, and it has several possible causes ranging from a blocked vent (a 5-minute fix) to a …