Dacor Oven Error Code U34

The U34 error code on a Dacor oven indicates that temperature sensor probe 3 in the upper or single oven cavity has developed an open circuit condition. The control system monitors the analog-to-digital (A/D) conversion value from the temperature probe continuously. When that A/D value reaches 0X3F0 or higher and remains at that level for 60 consecutive seconds, the control interprets this as a broken or disconnected probe and triggers the U34 fault. An open circuit in the probe circuit pushes the A/D reading to its upper limit, which is how the control distinguishes a sensor failure from a normal high-temperature reading.

The temperature sensing system relies on a resistance-based probe, typically an RTD or thermistor type, whose resistance changes predictably with temperature. An open probe means the circuit is broken somewhere between the probe itself and the relay board, which can occur at the probe element, the wiring harness, or the connectors at either end. The relay board processes the probe signal, so a failed connection at that board can produce the same A/D fault condition even if the probe element is physically intact.

Diagnosis begins at the relay board by inspecting the probe connector for loose, corroded, or damaged pins. The probe should then be tested directly at its connector to determine whether the element itself has failed. If connections are secure and the probe tests as open (infinite or extremely high resistance), the probe requires replacement. If the probe tests correctly but the fault persists, the wiring harness running between the probe and the relay board should be inspected for breaks, pinched sections, or heat damage and replaced if compromised.