Dacor Range Oven Cooktop Error Code U42

The U42 error code on a Dacor range or oven signals a failure detected on the relay board serving the upper or single oven cavity. The relay board is a dedicated control sub-board that receives switching commands from the main control board and uses electromechanical or solid-state relays to route power to the bake element, broil element, convection fan, and other high-voltage oven components. When the control system detects an abnormal condition on this relay board, such as a relay stuck open or closed, a failed switching output, or a loss of communication or feedback, it triggers the U42 fault to protect the appliance and alert the technician.

Relay board failures on Dacor ovens can stem from several root causes. Physical relay failure is common, where the relay contacts weld together under high current or simply wear out over time. Overheating inside the control compartment can degrade solder joints or damage onboard components. Power surges or voltage spikes traveling through the supply line can also damage relay board circuitry. In some cases, the wiring harness connecting the main control board to the relay board may develop an open circuit, a short, or a corroded connector that mimics a board failure.

Diagnosing U42 requires careful inspection of the relay board for visible burn marks, damaged components, or failed solder joints. The wiring harness and connectors between the main control board and the relay board should be checked for continuity and secure seating. If the board and wiring appear intact, the relay board itself is the primary suspect and typically requires replacement. This repair involves working with line-voltage components, so it should only be performed by a qualified technician with the appliance fully disconnected from power.