10 components coveredField manual · Furnace
Trane / American Standard S9X1 and S9X2 96% condensing gas furnaces: quick sheet
Covers: Trane and American Standard S-Series condensing gas furnaces: S9X1 (single-stage, now sold by Trane as the '96 Single-Stage') and S9X2 (two-stage, now the '96 Two-Stage'). American Standard sells the same model numbers (S9X1 listed as Silver by distributors; S9X2 placed in Gold by the brochure). Model pattern: S9X1 or S9X2 + width letter (B 17.5 in, C 21 in, D 24.5 in) + input MBH (040-120) + U (upflow/horizontal) or D (downflow/horizontal) + blower size digit (3, 4, 5) + PS + revision letters, e.g. S9X1B060U4PSB, S9X1D120D5PSBA, S9X2B040D3PSB, S9X2D120U5PSB. Search terms: S9X1, S9X2, Trane 96 single stage, Trane 96 two stage. Does NOT cover the S9V2 / S9V2-VS variable-speed models (separate sheet).
The S9X1 and S9X2 are Trane's condensing (up to about 96% AFUE) gas furnaces, 34 in tall, with a stainless steel tubular primary heat exchanger and a stainless secondary (condensing) heat exchanger, a silicon nitride hot surface igniter and a constant-torque ECM blower. The S9X1 is single-stage; the S9X2 is two-stage (two-stage gas valve and staged pressure switching). Each cabinet is dedicated upflow/horizontal (U) or downflow/horizontal (D). Faults are reported by the self-diagnostic integrated furnace control (IFC) through the door window; many condensing-furnace faults trace back to the condensate trap and drain.
Safety first
- Gas valve, manifold pressure, burners, heat exchangers and PVC vent/intake repairs are blocked: refer to a licensed gas technician.
- A rollout trip or water coming from the heat exchanger area: shut down, check CO and refer.
- Never jumper a limit, rollout or pressure switch.
- Lock out 120 V before touching wiring.
How it works
On a W call the IFC proves the pressure switch open, runs the inducer, waits for the switch to close, purges, heats the igniter and opens the gas valve; flame is proven by the flame sensor or the board retries and then locks out.
Flue gas passes the stainless primary exchanger and then the secondary exchanger, where water vapor condenses. Condensate drains through the trap in the vestibule and must flow freely; a full trap or blocked drain backs water into the inducer/collector and makes the pressure switch open.
S9X2: the furnace normally starts on low fire and moves to high fire on W2 or on the board timer when a single-stage thermostat is used. A second pressure-switch stage proves the higher draft before high fire.
The constant-torque ECM blower (Vortica II wheel on S9X1 per Trane) runs the heat and cool taps selected at the board. The control is a 24 V IFC compatible with standard thermostats (not communicating).
Components & tests
Unlock all 10 components, specs, service mode and teardown
Full library + AI assistant + the OnCall Tech app for iPhone & Android. $34.90, one time.
Get lifetime accessOfficial manufacturer documentation
Always confirm values against the tech sheet for the exact model.
OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work. © 2026 OnCall Tech. Original content; not a reproduction of any manufacturer document.Generic part photos (not of this brand): Condensing gas furnace with PVC vent pipes and metal ductwork in a utility room by Wtshymanski, CC BY-SA 4.0
