Furnace LED shows code 12 (blower on after power up) and blower may run briefly; furnace may not start heating immediately.

Note: On many Keeprite furnaces, code 12 is informational and not a fault.

Steps:

• Wait one full cycle: After restoring power, allow the furnace a few minutes to complete its self-check and blower purge. Then raise the thermostat to call for heat.
• Observe sequence: Verify that the inducer starts, pressure switch closes, ignitor glows, burners light, and blower starts. If all steps occur, no repair is needed.
• Check for other codes: If code 12 alternates with another fault code, troubleshoot the other code first.

If the furnace never progresses beyond code 12 and does not respond to a heat call, have a technician check the control board logic and thermostat circuit.