Code 42, inducer running when it should be off or not responding correctly

Safety first: Turn off power before accessing the control board or inducer wiring.

• Step 1 – Observe behavior: Note whether the inducer runs continuously or fails to start when called.
• Step 2 – Inspect wiring: Check the inducer plug and wires at the board and motor for burns, loose connections, or damage.
• Step 3 – Power cycle: Turn power off for several minutes, then restore. If the inducer immediately runs with no call for heat, the board relay is likely stuck.
• Step 4 – Professional testing: A technician should test inducer current draw and board output to confirm whether the motor or board needs replacement.