 
 
				Responded to no-heat complaint on 12-year-old Lennox furnace. Diagnostic revealed error codes HA478 and E126, with circuit board failure evident upon inspection. Further examination identified potential perforations in the heat exchanger with visible rust staining along seams. Documented defective components with photos. Furnace requires both control board replacement and heat exchanger evaluation. Customer advised of repair options and replacement recommendation due to equipment age and condition.
 
                                