Furnace LED displays code 42; inducer may not start or may run erratically.

Safety: Turn off power and gas. Inducer assemblies are part of the combustion system; improper work can cause CO hazards.

Homeowner checks:

• Listen for inducer: On a call for heat, note whether the inducer starts. No sound suggests motor or control issue.
• Inspect vent termination: Ensure the exhaust vent is not blocked outside.
• Check pressure tubing: Verify tubing to the pressure switch is intact and connected.

When to call a pro: A technician should test inducer voltage, motor operation, and pressure switch response, and replace the inducer assembly or pressure switch as needed.