9 components coveredField manual · Furnace
Carrier / Bryant 80% gas furnaces (58ST, 58SB, 58SC, 312/315 families): quick sheet
Covers: Carrier, Bryant and Payne non-condensing (80% AFUE) single-stage and two-stage upflow/multipoise furnaces with an amber status LED and two-digit status codes. Covers families such as Carrier 58ST/58SB/58SC and Bryant 312/315. Newer communicating and variable-speed boards add codes not listed here.
Carrier-family furnaces report faults as two-digit status codes flashed on an amber LED, read through the sight glass in the blower door. The first digit is a series of short flashes and the second digit a series of long flashes (for example 3 short + 1 long = code 31). The code legend is also printed on the inside of the blower door. Removing power clears the stored code, so read it before cutting power.
Safety first
- Gas valve, manifold pressure, burners, heat exchanger and venting repairs are blocked: refer to a licensed HVAC/gas technician.
- Read the status code before cutting power; then lock out 120 V before touching wiring.
- A rollout trip can mean flue gases are spilling: do not reset repeatedly, check CO and refer.
- Never jumper a limit, rollout or pressure switch to keep a furnace running.
How it works
On a W call the board first checks that the pressure switch is open, then starts the inducer. When the draft pressure switch closes, the board runs a short pre-purge, powers the hot surface igniter for its warm-up period, then opens the gas valve for the trial for ignition. The flame sensor must prove flame within the trial period or the board shuts the valve and retries.
After flame is proven the board waits through the heat-on delay and starts the blower at heating speed. At the end of the call the gas valve closes, the inducer runs a short post-purge and the blower continues for the selectable heat-off delay. Two-stage models use a second (high-fire) pressure switch and a two-stage gas valve.
The limit circuit (main limit, rollout switches and on some models a draft safeguard) is wired in series. If the limit circuit opens during a call the board drops the gas valve and runs the blower. Repeated limit trips in one call cause a limit lockout (code 13). Repeated ignition failures cause ignition lockout (code 14). These lockouts typically clear on their own after a set period or when power is cycled.
Status LED behaviour: code 11 means no previous code is stored. Code 12 appears when the furnace is powered up during a heat call and the blower runs a fixed period before the normal sequence starts. Because stored codes are erased when power is removed, always count the flashes before opening the disconnect.
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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.
