Dacor Range Oven Cooktop Error Code U25

The U25 error code on Dacor ranges and ovens indicates an over-temperature condition in the upper or single oven cavity, specifically caused by a shorted ambient temperature probe located on the relay board. The ambient temperature probe is a thermistor-type sensor mounted directly on the relay board that monitors the internal temperature of the control electronics, not the oven cavity itself. When this probe shorts, it sends an abnormal signal to the control board, which interprets the reading as a dangerously high ambient temperature condition and triggers the U25 fault to protect the electronics from thermal damage.

The relay board is a critical component in Dacor ovens that manages the switching of heating elements, broil elements, and convection systems based on commands from the main control board. The ambient temperature probe integrated into or connected to this relay board acts as a safeguard, ensuring the board's operating environment stays within safe limits. A shorted probe will produce a resistance reading that falls outside the expected range, causing the control system to flag the condition immediately, regardless of the actual oven temperature.

Common causes of this fault include a failed thermistor probe due to heat stress or age, damaged wiring between the probe and the relay board, a corrupted solder joint at the probe connection point, or a relay board that has itself failed and is generating an incorrect signal. Because the probe is physically integrated with or closely tied to the relay board assembly, diagnosis often involves inspecting the wiring harness for shorts to ground and testing the probe's resistance. If the probe tests as shorted, the relay board or the probe assembly will typically need to be replaced.