7 components coveredField manual · Furnace
ICP 80% gas furnaces (Heil, Tempstar, Comfortmaker, KeepRite, Arcoaire): quick sheet
Covers: International Comfort Products (ICP, a Carrier company) non-condensing single-stage furnaces such as the N8MSN / N8MPN style models, sold under several brand names with the same control board. Single LED flashing in groups.
ICP furnaces are badged under many names but share boards and parts. The LED shows a heartbeat (slow pulse) when idle and flashes continuously during a call; fault codes are counted groups. Record the code before removing the blower door or power, which clears it.
Safety first
- Gas valve, burners, heat exchanger and venting are blocked: refer to a licensed HVAC/gas technician.
- Rollout trips are a CO risk: do not bypass or keep resetting.
- Lock out 120 V before touching wiring.
How it works
On a heat call the board checks the pressure switch is open, starts the inducer, waits for the switch to close, pre-purges, heats the hot surface igniter and opens the gas valve. Flame is proven by the flame sensor.
The blower starts after the heat-on delay; at the end of the call the inducer post-purges and the blower runs its off delay.
Limit circuit trips repeated within one call cause a limit-circuit lockout that resets on its own after a timed period. A gas heating lockout (8 flashes) does not auto-reset and needs a power reset after the cause is fixed.
A steady LED (not flashing) is a control lockout state, not a normal condition.
Components & tests
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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.
