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Error code reference

Dacor Oven Error Code U23

Upper/single oven ambient over temperature

Dacor codesDacor oven codes

Upper/single oven ambient over temperature - thermistor on relay board has registered over 80°C.

First step from the service manual

Verify exhaust area, inlet at bottom of door, and inlet grill are free from blockages. Run oven in normal mode and verify temperatures are normal.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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What U23 means on a Dacor oven

The U23 error code on a Dacor oven indicates that the ambient temperature inside the upper or single oven cavity has exceeded 80°C (176°F) as measured by the thermistor located on the relay board. This thermistor is not the same as the oven temperature sensor used to regulate cooking temperatures. Instead, it monitors the internal ambient environment around the control electronics and relay board to protect those components from heat damage. When this thermistor reading climbs above the 80°C threshold, the oven triggers U23 as a protective fault.

The most common root cause is restricted airflow through the oven's ventilation path. Dacor ovens rely on specific airflow channels, including the exhaust area at the rear or top, the inlet at the bottom of the door, and the inlet grill, to circulate cooling air around the electronics. If any of these openings are blocked by debris, grease buildup, or improper installation clearance, heat accumulates in the relay board area and the thermistor registers an over-temperature condition.

In some cases, blocked vents are not the issue and the fault points instead to a failing thermistor on the relay board itself, a malfunctioning cooling fan, or a relay board that is generating excessive heat due to component failure. Verifying that the oven operates at normal cooking temperatures in standard mode is an important early step, since abnormal cooking temperatures alongside U23 would suggest a broader thermal management or control board problem rather than a simple airflow blockage.

Source: manufacturer service documentation.

Common causes of U23

  1. 01

    Blocked ventilation openings

    Wiring / connection

    Grease, debris, or objects obstructing the exhaust area, the inlet at the bottom of the door, or the inlet grill restrict cooling airflow and allow heat to build up around the relay board. Inspect all three ventilation points and clear any blockages before running the oven again.

  2. 02

    Insufficient installation clearance

    Wiring / connection

    If the oven was installed without adequate clearance around the ventilation openings, airflow is permanently restricted regardless of whether the vents themselves are clean. Verify that installation dimensions meet Dacor specifications for the unit.

  3. 03

    Faulty or failing cooling fan

    Part replacement

    The cooling fan circulates air through the electronics compartment and keeps the relay board within safe temperature limits. A fan that is running slowly, intermittently, or not at all will cause ambient temperatures to rise and trigger U23.

  4. 04

    Defective relay board thermistor

    Part replacement

    The thermistor mounted on the relay board can drift out of calibration or fail, reporting falsely elevated temperatures even when actual conditions are normal. If airflow is confirmed clear and the oven heats correctly, a faulty thermistor is a likely cause.

  5. 05

    Relay board failure

    Part replacement

    A relay board that has a failing component can generate excess heat internally, driving the thermistor reading above the 80°C limit. This is typically accompanied by other control or heating irregularities.

See the test procedure for each cause

Frequently asked questions about U23

What does U23 mean on a Dacor oven?
U23 means the thermistor on the relay board in your upper or single oven has detected an ambient temperature above 80°C (176°F). This is a protective fault that monitors heat levels around the oven's control electronics, not the cooking cavity temperature. It is triggered when cooling airflow is insufficient or when a component in the electronics area is failing. The oven generates this code to prevent heat damage to the relay board and related parts.
Can I fix U23 on my Dacor oven myself?
In many cases, yes. Start by checking the exhaust area, the inlet at the bottom of the door, and the inlet grill for any blockages such as grease buildup or debris, and clear them if found. After clearing the vents, run the oven in normal mode and confirm it heats correctly. If the code returns after the vents are clean and clearances are correct, diagnosing or replacing the cooling fan, thermistor, or relay board will likely require a qualified technician.
Is it safe to use my Dacor oven while U23 is displayed?
It is not recommended to continue operating the oven while U23 is active. The code indicates that the electronics area is overheating, which can cause damage to the relay board and control components if the oven continues running. Address the ventilation or component issue first before using the oven again.
Will resetting the oven clear the U23 error code?
A reset may temporarily clear the U23 code, but if the underlying cause, such as a blocked vent or a failing component, has not been resolved, the fault will return once the relay board thermistor reaches 80°C again. Always address the root cause before relying on a reset as a solution.
How much does it cost to repair a Dacor oven showing U23?
If the fault is simply blocked vents, the repair costs nothing beyond cleaning time. If a cooling fan needs replacement, parts and labor typically range from $150 to $350. Relay board replacement is generally more expensive, often falling in the $300 to $600 range depending on the specific model and labor rates in your area. Getting a diagnostic call from a certified Dacor technician, usually $75 to $150, will help identify the exact faulty component before committing to parts costs.

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