Lennox Error Code 271

Priority condition: Service Urgent The furnace is in Watchguard mode. The furnace low pressure switch is open. This is a five strike condition during a single demand. • Check pressure (inches w.c.) of low pressure switch closing during a heat call. • Measure operating pressure (inches w.c.). • Check for blocked cold end heater box (CEHB), or condensate drain or drain strainers at outlet of CEHB and cracked hoses. • Check for cracked hoses. • Check levelness of unit. NOTE: Check Service Manual and Service and Application Note H-13-07 “Condensing Furnace Pressure Switch Troubleshooting” for additional information.