Furnace blower starts and stops repeatedly without burner ignition; cool air may blow briefly.

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

Steps:

• Verify thermostat mode: Ensure the thermostat is not in a fan-circulate mode that periodically runs the blower.
• Check for error codes: Observe the control board LED for any stored codes indicating limit or other faults.
• Inspect limit wiring: Ensure connections to the high limit switch are secure and not intermittently opening.

When to call a technician: If the blower cycles without clear thermostat commands and no codes, the control board or limit circuit may need professional testing.