Gree Mini Split U8 Error Code

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

Check your model first

  • Series using the exhaust-sensor mapping

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

Quick answer

U8 means the outdoor unit is not receiving a valid zero-crossing signal from the indoor unit - usually indoor/outdoor wiring, a loose low-voltage connector, or a board fault. Check wiring and power cycle once; boards are technician work.

Severity: medium · DIY difficulty: intermediate

Safety

Stop at visual wiring checks and one reset. Do not open either unit's panels or test live boards and sensors. Technician-only.

What U8 means

U8 means the outdoor unit detected an indoor-unit zero-crossing signal fault - the AC zero-cross timing reference from the indoor unit is missing or invalid, so the drive cannot synchronize. Gree tables also associate U8 with exhaust-temperature sensor disconnection on some series; both readings are technician-level faults.

Code meaning varies by series

  • Series using the exhaust-sensor mapping: Exhaust temperature sensor disconnection / zero-cross detection of indoor circuit

Causes, ranked

  1. 1. Indoor/outdoor communication wiring or terminal problem common DIY

    Check: Visually check the interconnecting cable at both ends for damage, chewed insulation, or loose strain relief (do not disconnect live wires).

    Fix: If damage is visible, schedule service; otherwise power cycle once and retest.

  2. 2. Loose low-voltage connector after service or vibration occasional pro only

    Check: Connectors are inside the units.

    Fix: Technician: reseat the low-voltage connectors.

  3. 3. Exhaust temperature sensor disconnection (series using this mapping) occasional pro only

    Check: Sensor testing only.

    Fix: Technician: test and replace the exhaust sensor.

  4. 4. Indoor or outdoor control board fault after wiring is verified rare pro only

    Check: Board-level diagnosis only.

    Fix: Technician: diagnose both boards.

Related codes

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

Gree U9 · Gree E6 · Gree U5 · Gree F0

Commonly searched as: "gree u8" · "gree error code u8" · "gree air conditioner u8"

Sources

Related Mini Split guides

Mini-Split Communication Error: DIY Checks · Mini-Split Flashing Light Decoder: Blink Patterns · How to Reset a Mini-Split After a Power Outage · Mini-Split Sensor Errors: How to Test a Thermistor