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Error code reference

Sanyo Air Conditioner Error Code UU

DC over current.

Sanyo codesSanyo air conditioner codes

DC over current.

First step from the service manual

Replace outdoor main board.

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

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What UU means on a Sanyo air conditioner

The UU error code on a Sanyo air conditioner indicates a DC overcurrent fault within the outdoor unit. This occurs when the direct current flowing through the inverter drive circuit or compressor motor windings exceeds safe operating thresholds. The outdoor main board continuously monitors current levels in the DC bus and motor drive circuit. When current spikes beyond the programmed limit, the board triggers a protective shutdown and displays UU to prevent damage to the compressor, IPM (Intelligent Power Module), or associated drive components.

The most common source of this fault is a failure within the outdoor main board itself, which is why board replacement is the primary diagnostic step. The board houses the IPM and current sensing circuitry, and a degraded or failed IPM can produce false overcurrent readings or allow uncontrolled current surges. Beyond the board, a mechanically seized or electrically shorted compressor can draw excessive current during startup or operation, triggering the same fault. Wiring faults between the board and compressor, including insulation breakdown or loose connections, can also cause momentary overcurrent conditions.

Before replacing the outdoor main board, a technician should inspect wiring harnesses for visible damage, check compressor terminals for shorts to ground using a megohmmeter, and verify that the power supply voltage is within specification. If compressor resistance readings are normal and the power supply is stable, the outdoor main board is the most probable failed component and should be replaced to resolve the UU fault.

Source: manufacturer service documentation.

Common causes of UU

  1. 01

    Failed outdoor main board or IPM

    Part replacement

    The Intelligent Power Module on the outdoor main board can fail and cause uncontrolled current surges or false overcurrent readings. Board replacement is the primary diagnostic step for this error.

  2. 02

    Compressor electrical fault

    Part replacement

    A shorted or grounded compressor winding will draw excessive DC current and trigger the UU code. Use a megohmmeter to check compressor terminals for shorts to ground and measure winding resistance to identify this condition.

  3. 03

    Seized compressor

    Part replacement

    A mechanically locked compressor will pull a high locked-rotor current at startup, exceeding the overcurrent threshold. This is often accompanied by unusual noise or a complete failure to start.

  4. 04

    Wiring fault or loose connection

    Wiring / connection

    Damaged insulation, corroded terminals, or loose connections in the wiring between the main board and compressor can cause intermittent overcurrent spikes. Inspect the harness and terminal connections at both the board and compressor.

  5. 05

    Low or unstable supply voltage

    Wiring / connection

    Insufficient or fluctuating input voltage to the outdoor unit can cause the drive circuit to compensate with higher current draw, triggering the fault. Verify supply voltage at the disconnect under load conditions.

See the test procedure for each cause

Frequently asked questions about UU

What does UU mean on a Sanyo air_conditioner?
The UU code on a Sanyo air conditioner indicates a DC overcurrent fault in the outdoor unit. The system has detected that current in the inverter drive circuit or compressor motor has exceeded safe limits. The unit shuts down automatically to prevent damage to the compressor and drive components. The outdoor main board is the first component to evaluate when this code appears.
Can I fix the UU error code myself?
Diagnosing and repairing the UU error typically requires technical knowledge of inverter drive circuits and safe handling of high-voltage DC components. A knowledgeable technician should inspect the outdoor main board, compressor windings, and wiring. Replacing the outdoor main board is the recommended first step, but compressor testing requires specialized tools such as a megohmmeter.
Is it safe to keep using my air conditioner when the UU code appears?
No. The UU code represents an active protective shutdown triggered by an overcurrent condition. Continuing to operate the unit or bypassing the fault could result in permanent damage to the compressor or outdoor main board. Leave the unit off and have it inspected by a qualified technician before attempting to restart it.
Will resetting the air conditioner clear the UU error?
A power reset may temporarily clear the UU code and allow the unit to restart, but if the underlying fault persists, the error will return, often quickly. Resetting without addressing the root cause risks further damage to the compressor or drive board. A proper diagnosis should be performed rather than relying on repeated resets.
How much does it cost to repair a UU error on a Sanyo air conditioner?
Repair costs vary depending on the failed component. Outdoor main board replacement typically ranges from $200 to $500 including parts and labor. If the compressor has failed, costs can range from $600 to over $1,500 depending on the unit size and compressor availability. A technician inspection will be needed to determine which component is at fault before an accurate estimate can be given.

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