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Error code reference

Dacor Range Oven Cooktop Error Code U21

Over temperature (upper/single oven)

Dacor codesDacor range oven cooktop codes

Over temperature (upper/single oven) - clean temp over 890°F.

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  • Step-by-step tests with expected resistance, voltage, and continuity values
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  • Verified part numbers when replacement is required
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What U21 means on a Dacor range oven cooktop

The U21 error code on Dacor ranges and ovens indicates an over-temperature condition in the upper or single oven cavity during a self-clean cycle. Specifically, this fault triggers when the oven's internal temperature exceeds 890 degrees Fahrenheit, which is beyond the safe operating threshold for the self-clean mode. The control board monitors cavity temperature continuously through a temperature sensor (RTD probe), and when readings climb past this limit, U21 is generated to halt the cycle and protect the unit from thermal damage.

The most likely culprits behind this fault are a failed or drifting oven temperature sensor, a malfunctioning control board that is misreading sensor data, or a door latch assembly that is not sealing the oven cavity properly during the clean cycle. A failing sensor may send inaccurate high-temperature readings to the control board, triggering the fault even when actual cavity temperatures are within range. Conversely, a faulty door seal or latch can allow heat to escape unevenly, causing the oven to overwork and genuinely exceed safe temperature thresholds.

The oven's thermal limiter or high-limit thermostat is also a component to evaluate, as these safety devices are designed to cut power to the heating elements when extreme temperatures are detected. If the limiter has tripped or failed, it can contribute to erratic temperature behavior during the self-clean cycle. Technicians should use a multimeter to check the resistance of the temperature sensor at room temperature, which should typically read approximately 1080 ohms at 77 degrees Fahrenheit for standard RTD probes used in Dacor units, and compare control board outputs against expected voltage ranges.

Source: manufacturer service documentation.

Common causes of U21

  1. 01

    Faulty oven temperature sensor (RTD probe)

    Part replacement

    A drifting or failed RTD sensor can send inaccurate high-temperature readings to the control board, falsely triggering the U21 fault. Check the sensor's resistance with a multimeter at room temperature, expecting approximately 1080 ohms at 77 degrees Fahrenheit.

  2. 02

    Oven door not sealing properly during self-clean

    Part replacement

    A worn door gasket or a door latch that does not engage fully can allow excessive heat buildup or uneven temperature distribution during the self-clean cycle. Inspect the door gasket for tears, brittleness, or gaps, and confirm the latch locks completely.

  3. 03

    Tripped or failed thermal limiter (high-limit thermostat)

    Part replacement

    The high-limit thermostat is a safety component that cuts power to heating elements when temperatures become dangerously high. If it has tripped or failed in a closed position, it can cause erratic temperature behavior that pushes the cavity beyond the 890 degree threshold.

  4. 04

    Control board malfunction

    Part replacement

    A faulty control board may misinterpret sensor data or fail to regulate the heating elements properly during the self-clean cycle, resulting in uncontrolled temperature rise. If the sensor and thermal limiter test correctly, the control board should be evaluated.

  5. 05

    Shorted or stuck heating element

    Part replacement

    A bake or broil element that is shorted or stuck in an energized state can continuously add heat to the oven cavity with no regulation, causing temperatures to climb past the 890 degree limit during self-clean.

See the test procedure for each cause

Frequently asked questions about U21

What does U21 mean on a Dacor range, oven, cooktop?
The U21 code on a Dacor oven indicates that the upper or single oven cavity exceeded 890 degrees Fahrenheit during the self-clean cycle. This is a safety fault that automatically stops the cleaning process to prevent thermal damage to the appliance. The oven needs to cool down fully before any further diagnostics or operation. Common causes include a faulty temperature sensor, a poor door seal, or a malfunctioning control board.
Is it safe to use my Dacor oven after a U21 error?
You should not attempt to run the self-clean cycle again until the underlying cause of the U21 fault has been identified and corrected. Normal baking and cooking may be possible after the oven has fully cooled and the error has been cleared, but running the self-clean mode again without repair risks repeating the over-temperature event. If the temperature sensor or thermal limiter has failed, the oven may also behave erratically during normal cooking, so a technician inspection is strongly recommended before continued use.
Will resetting my Dacor oven clear the U21 error code?
Resetting the oven by cutting power at the circuit breaker for several minutes may temporarily clear the U21 code, but it will not fix the underlying problem that caused the over-temperature fault. If the faulty component, such as a worn door gasket, drifting temperature sensor, or tripped thermal limiter, is not addressed, the U21 code will return the next time the self-clean cycle is attempted. A reset should only be used as a first step in diagnostics, not as a permanent fix.
How do I fix a U21 error on a Dacor oven?
Start by allowing the oven to cool completely, then check the oven temperature sensor by measuring its resistance with a multimeter, looking for approximately 1080 ohms at room temperature. Inspect the door gasket for damage and confirm the door latch engages fully during the self-clean cycle. If those components appear normal, a technician should evaluate the thermal limiter, heating elements, and control board. Parts like the RTD sensor and door gasket are generally straightforward replacements, while control board replacement requires more advanced diagnosis.
How much does it cost to repair a Dacor oven showing a U21 error?
Repair costs for a U21 fault vary depending on the failed component. A replacement oven temperature sensor typically costs between 30 and 80 dollars for the part, while a door gasket or latch assembly can range from 20 to 100 dollars. Control board replacement is the most expensive scenario, often ranging from 200 to 500 dollars or more for parts alone. Adding professional labor, total repair costs can range from 100 dollars for a simple sensor swap to 600 dollars or higher for a control board replacement.

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