Gree Mini Split U3 Error Code

Updated 2026-08-29 · review status: manual-verified · reviewed by MiniSplitDecoder Editorial Team Last verified: 2026-08-29

Check your model first

The source record does not specify an exact model family.

Match the model on your equipment label to the linked manufacturer documentation. The same code can mean different things across model families.

Quick answer

U3 means the DC bus-bar voltage dropped below the protection limit - usually a supply-power problem, weak reactor, or drive-board fault. Try one reset and check supply quality; the bus-bar itself is technician territory.

Severity: high · DIY difficulty: intermediate

Safety

Stop at the single power-cycle and supply check. The DC bus bar holds lethal stored charge even when powered off - never open the electrical box. Technician-only.

What U3 means

U3 means the outdoor unit detected DC bus-bar (P-N) voltage drop protection. The inverter's DC supply sagged below limits, typically from a power-quality event, loose power wiring, a failing reactor/PFC stage, or a drive-board fault.

Causes, ranked

  1. 1. Mains supply sag, brownout, or momentary outage common DIY

    Check: Power cycle once and note whether lights/other appliances flicker at the same time.

    Fix: If supply is unstable, an electrician (not the HVAC tech) should check the circuit.

  2. 2. Loose power input or reactor connection occasional pro only

    Check: Terminal inspection is inside the outdoor electrical box.

    Fix: Technician: inspect and retermine power input and reactor wiring.

  3. 3. Failing PFC/reactor stage or drive-board fault occasional pro only

    Check: Requires bus-bar voltage measurements.

    Fix: Technician: diagnose the PFC stage and drive board.

  4. 4. Compressor overload dragging the bus down after power checks pass rare pro only

    Check: Compressor testing only.

    Fix: Technician: test the compressor and drive under load.

Related codes

Cross-references for the same fault family, by brand:

Gree U1 · Gree U2

Commonly searched as: "gree u3" · "gree error code u3" · "gree air conditioner u3"

Sources

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