Checked the furnace for the east side of home Found error code for loss of flame Checked and cleaned the flame sensor, 4.5 reading after cleaning, furnace was in the laundry room also can cause extra buildup on the sensor Checked the flue piping, b-vent needs to be insulated, temperature difference is causing condensation Owner will try to insulate himself Insured the furnace is currently working before leaving Made owner aware small chance the control board could be bad, I’m the same error code happens again he will need an estimate