Gree Error Code U0: Compressor preheat not finished (Heat Pump)

Updated October 13, 2026 · by Aurora Star Tech Inc.

Gree error code U0 on a heat pump means: Compressor preheat not finished. It is also called Gree diagnostic code U0.

Low severityHeat PumpGree GMV6 Mini VRF

Homeowner? What Gree code U0 means for you

Usually minor Your heat pump is reporting: Compressor preheat not finished. This code is usually informational or minor. The safe checks below often clear it; call us if it keeps showing up.

Safe things you can check yourself

Check the thermostat: right mode (Heat or Cool), set a few degrees past room temperature, and fresh batteries if it uses them.
Check both breakers and the outdoor disconnect box beside the outdoor unit; all should be ON.
Look at the air filter. If it is grey and clogged, replace it; a blocked filter causes many shutdowns.
In winter, keep snow and ice off and away from the outdoor unit. A short defrost cycle with steam is normal.
Try one reset: turn the power off for 30 seconds, then back on. If the code comes back, stop resetting and call a technician.

Call (647) 657-2977 Book a service call

Licensed technicians serving Vaughan, Toronto and the GTA.

What does Gree error code U0 mean?

Compressor crankcase warm-up time is not complete (8 h needed before startup).

Applies to: Gree GMV6 Ultra Heat Mini VRF 36-60k (GMV-V..WL/C-T(U))

Common causes of Gree code U0

Power applied too recently

Safety: Gas, electrical and refrigerant work must be done by a licensed technician. Turn off power and gas before servicing, never bypass a safety control, and always follow the manufacturer's manual for your exact model.

Gree models that use code U0

GMV-V36WL/C-T(U)GMV-V48WL/C-T(U)GMV-V60WL/C-T(U)

Other Gree Heat Pump codes

Code	Meaning
PF	Compressor drive charging circuit fault
PH	DC bus voltage too high
PJ	Inverter compressor failed to start
PL	DC bus voltage too low
PP	Inverter compressor AC current protection
PU	DC bus capacitor charging fault
U1	Compressor phase current sensing fault
U2	Outdoor capacity code / jumper wrong
U3	DC bus voltage drop
U4	Refrigerant shortage at startup
U5	Whole-unit current sensing fault
U6	Service valves not opened

All Gree Heat Pump error codes →

Gree code U0: homeowner questions

What does Gree code U0 mean?

Compressor preheat not finished. Compressor crankcase warm-up time is not complete (8 h needed before startup).

Is it safe to keep using my heat pump with code U0?

Usually yes. Code U0 is normally minor, but if it keeps coming back have it checked.

Can I reset Gree code U0 myself?

You can try one reset (power off for 30 seconds, then on). If Gree code U0 comes back, the cause is still there and a licensed technician should check it.

Who can fix Gree code U0 near me?

Aurora Star Tech Inc. repairs Gree heat pumps in Vaughan, Toronto and across the GTA. Call (647) 657-2977 or book a service call online.

Homeowner help: AC Running But Not Cooling: What to Check · Heat Pump Not Heating or Blowing Cold Air

Troubleshooting guides

Compressor will not run - Gree ductless Gree · Heat Pump
Louver will not swing - Gree ductless Gree · Heat Pump
Noise or vibration - Gree ductless Gree · Heat Pump
Outdoor fan will not run - Gree ductless Gree · Heat Pump
Unit will not start - Gree ductless Gree · Heat Pump
Water leaking from indoor unit - Gree ductless Gree · Heat Pump
Weak cooling or heating - Gree ductless Gree · Heat Pump

Source: Gree GMV6 Ultra Heat Mini VRF 36-60k (GMV-V36-48-60WL-C-T(U)) service.pdf - section Chapter 3 Faults, 4.1 Error Indication. Written in our own words as a summary; always check the original manual.

General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.