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Error code reference

A.O. Smith Water Heater Error Code 14

Temperature sensor (thermistor) inside the immersion probe is shorted.

A.O. Smith codesA.O. Smith water heater codes

Temperature sensor (thermistor) inside the immersion probe is shorted.

First step from the service manual

Turn power off for 10 to 20 seconds then on again to clear the error code.

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

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What 14 means on a A.O. Smith water heater

Error code 14 on an A.O. Smith water heater indicates that the temperature sensor thermistor located inside the immersion probe has developed a short circuit condition. The immersion probe assembly is inserted directly into the water heater tank and contains a thermistor that continuously monitors water temperature. When this thermistor shorts internally, its resistance drops to near zero, which the control board interprets as an impossibly high temperature reading. This triggers the fault code as a safety measure to prevent further operation under false temperature data.

The thermistor inside the probe operates by varying its electrical resistance in proportion to temperature. Under normal conditions, the control board reads this resistance to determine actual water temperature and regulate heating cycles accordingly. A shorted thermistor produces a resistance signal that falls outside the expected operating range, making accurate temperature regulation impossible. This is distinct from an open-circuit failure, which typically produces a different fault code.

The most immediate diagnostic step is to cycle power off for 10 to 20 seconds and then restore it. This allows the control board to reset and re-evaluate the sensor signal. If the fault returns immediately after the reset, the thermistor or its associated wiring is the likely cause and physical inspection of the probe assembly and its connector wiring is the next appropriate step.

Source: manufacturer service documentation.

Common causes of 14

  1. 01

    Failed thermistor inside the immersion probe

    Part replacement

    The thermistor element itself has shorted internally, which is the most direct cause of this fault. The probe assembly will need to be replaced if the thermistor has failed.

  2. 02

    Damaged or pinched sensor wiring

    Wiring / connection

    Wiring between the immersion probe and the control board can become pinched, abraded, or corroded, causing the conductors to contact each other and create a short. Inspect the full wire harness run from the probe connector to the board for visible damage.

  3. 03

    Corroded or contaminated probe connector

    Wiring / connection

    Moisture or mineral deposits inside the connector where the probe wiring plugs into the harness can bridge the terminals and simulate a short circuit. Inspect and clean the connector pins and housing.

  4. 04

    Transient electrical fault or power surge

    Wiring / connection

    A brief power surge or electrical disturbance can cause the control board to register a false short on the sensor input. Cycling power off for 10 to 20 seconds allows the board to reset and may clear the code if no physical damage occurred.

  5. 05

    Faulty control board sensor input

    Part replacement

    In less common cases, the control board's sensor monitoring circuit can fail and incorrectly report a thermistor short even when the probe and wiring test correctly. Board replacement would be required if all other components check out.

See the test procedure for each cause

Frequently asked questions about 14

What does 14 mean on a A.O. Smith water_heater?
Error code 14 means the temperature sensor thermistor inside the immersion probe has shorted. The control board detected a resistance value from the probe that indicates a short circuit condition rather than a valid temperature reading. As a result, the water heater shuts down because it cannot reliably monitor or control water temperature. Cycling the power off for 10 to 20 seconds and back on is the first step to attempt clearing the fault.
Will resetting the power clear error code 14 on my A.O. Smith water heater?
A power reset of 10 to 20 seconds will clear the fault if it was caused by a temporary electrical disturbance. If the thermistor or its wiring has a physical short, the code will return shortly after the reset. Repeated return of the fault after reset confirms a hardware problem that requires further diagnosis of the probe assembly and wiring.
How do I fix error code 14 on an A.O. Smith water heater?
Start by turning power off for 10 to 20 seconds and restoring it to check if the fault clears. If it returns, inspect the wiring harness from the immersion probe to the control board for damage, pinching, or corrosion. Also inspect the connector at the probe for contamination or corroded pins. If the wiring and connectors check out, the immersion probe assembly likely needs replacement.
Is error code 14 on an A.O. Smith water heater a safety concern?
The water heater shuts down when code 14 appears specifically as a safety measure, since it cannot accurately monitor water temperature with a shorted sensor. Operating without reliable temperature data could allow the water to overheat. The unit should not be forced back into operation if the fault continues to return after a reset.
How much does it cost to repair error code 14 on an A.O. Smith water heater?
If the fault clears with a power reset, there is no parts cost. Replacement of the immersion probe assembly typically runs in the range of $30 to $80 for the part, depending on the specific model. If a control board is ultimately needed, parts costs can range from $100 to $250 or more. Adding professional labor for diagnosis and repair generally brings total costs into the $150 to $400 range depending on the root cause.

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