Furnace inducer motor runs continuously but burners do not light and no code is shown.

Safety: Turn off power before testing switches or wiring.

Steps:

• Check thermostat circuit: Disconnect the W wire at the furnace. If the inducer stops, the thermostat or its wiring is calling for heat continuously.
• Test pressure switch: With power off and tubing removed, check continuity across the pressure switch. It should be open with no draft. If it reads closed, the switch is stuck and should be replaced.
• Inspect tubing: Ensure the pressure tubing is not pinched or misrouted causing false readings.

Note: If the inducer still runs with W disconnected and the pressure switch tests normal, the control board may be faulty.