What It Means
- Control self-check OKAY? NO branch: gas valve OFF, combustion air blower ON, indoor blower ON; both lamps alternating fast flash; check broken ignitor/open ignitor circuit.

Ducted Heating:
Control self-check not okay. Gas valve off, combustion air blower on, indoor blower on. Check for broken ignitor or open ignitor circuit.
Control self-check OKAY? NO branch: gas valve OFF, combustion air blower ON, indoor blower ON; both lamps alternating fast flash; check broken ignitor/open ignitor circuit.
Continue in ACLogics with guided diagnosis for your equipment and symptoms.