The Lennox 10J58 is the OEM-spec direct spark ignition (DSI) control board for Lennox brand furnaces. It manages the full ignition sequence -- pre-purge, spark ignition, and interpurge timing -- and features built-in LED diagnostic indicators to help pinpoint faults fast. Also cataloged under NBK Parts number 20334, this board is the correct replacement when your furnace fails to light, locks out, or shows ignition faults.
When a Lennox furnace stops igniting, the DSI control module is one of the first components to evaluate. This board governs spark timing, valve activation, inducer motor output, and safety lockout logic. Replacing it with the correct OEM-spec part -- Lennox 10J58 -- ensures the furnace operates within factory-defined timing and safety parameters.
The module is rated for a wide ambient temperature range of -40F to 160F, making it suitable for installations in unconditioned utility spaces and mechanical rooms that see extreme seasonal temperatures.
Onboard LED indicators display fault codes at the board, reducing diagnostic time without extra test equipment.
30-second pre-purge, 7-second ignition trial, and 30-second interpurge timing match Lennox factory specifications exactly.
Operates reliably from -40F to 160F -- handles cold utility closets and warm mechanical rooms without issue.
Meets ANSI Z21.20 automatic ignition system certification requirements for gas-fired heating appliances.
The 10J58 module controls the complete DSI sequence: the inducer motor is energized first, then the 30-second pre-purge clears the heat exchanger of residual gas. At the end of pre-purge, the gas valve and spark electrode are energized simultaneously for a 7-second ignition trial. If flame is not proven within that window, the module de-energizes the valve, waits through the 30-second interpurge period, and retries or locks out depending on configuration.
This hard-wired timing sequence is critical for proper, safe furnace operation and is one reason substituting generic ignition boards is risky -- timing parameters that differ even slightly from the Lennox specification can cause nuisance lockouts or unsafe ignition conditions.
The 10J58 control module mounts inside the furnace cabinet in the location of the original board. Standard wiring harness connectors are used -- match terminal labels carefully when transferring wires from the old board. Input power is 24VAC from the furnace transformer; line-voltage wiring for the inducer motor is routed separately and is 120VAC or 240VAC depending on the specific Lennox unit.