57: Pressure switch stuck open when it should be closed
Homeowner checks
The most-reported Rheem code: inducer runs, switch never proves. Vent, condensate, hose, switch — in that order.
From the table: 7-segment display codes (no blink counting) — source: Rheem 95P Series Installation Instructions, "Diagnostics and Fault Codes" (read the document, fetched 2026-10-30). Covers: Rheem 95P-series and the R801T generation: the control has a small digital display. Standby reads 0; running modes read as letters. Faults show as two-digit numbers, first digit for a second, second digit for a second, then a pause.
Rheem's wording is exact: "pressure switch stuck open when should be closed." Pair it with its mirror, code 55 — stuck closed when it should be open — and you can read the board's logic: at rest the switch must be open (55 checks that), after the inducer starts it must close (57 checks that). A 57 is a start-up that dies at the proof step.
The suspect order that falls out of the manual's world: the vent (terminal blockage, ice), the condensate (on these condensing furnaces a slow drain is a pressure fault in disguise), the hose (cracked or water-logged tubing lies to the switch), and finally the switch itself. The first two are yours to look at; the last two are a technician's.
Homeowner checks — the safe list:
- Go outside and look at the vent and intake pipes. Snow, ice, leaves, a nest, or a mulch pile against the terminal can cause exactly this code.
- On a condensing (90%+) furnace, check the condensate drain: a backed-up drain or frozen drain line trips the same switch.
- Air filter: a starved furnace is a furnace that overheats and behaves badly in several code families.
- Make sure the blower door is fully seated after you look at the light.
The five-minute lockout
Rheem's service literature adds a behavior worth knowing: if the pressure switch fails to close after 60 seconds of inducer run at the start of a cycle, the control starts a five-minute soft lockout, then tries again on its own. A Rheem that "fixes itself" for a while and reposts 57 is not haunted — it is cycling through that timer with a marginal draft.
The two rules that outrank everything on this page.
1. Smell gas? Stop reading. Leave the house and call your gas utility or 911 from outside. No code is worth diagnosing through a gas smell.
2. Never bypass a safety switch — no jumping a pressure switch, no taping a limit, no propping a rollout. Those switches are the only thing between a furnace fault and a fire or carbon-monoxide problem. This library explains codes; it does not teach repairs inside the cabinet.
One honesty note before the tables: codes change between control boards, sometimes inside the same brand and the same decade. Every table below names the board and the manual it was transcribed from. The chart glued inside your own blower door is the final word for your furnace — if it disagrees with this page, believe the door.