Gree Split AC Error Code U1 — What It Means & How to Fix It

What Does This Error Mean?

U1 means the inverter drive detected that the compressor rotor is losing its magnetic alignment. This can happen when the system is overloaded, in extreme heat, or when the compressor is ageing. A technician should assess whether the compressor needs service or replacement.

Affected Models

Gree FAIRY Series
Gree LOMO Series
Gree U-MATCH Series
Gree PULAR Series
Gree Inverter Split System

Common Causes

System overloaded — room too large for the AC capacity or extreme outdoor temperatures
High ambient temperature pushing the compressor beyond its rated operating range
Compressor motor reaching end of life and permanent magnet weakening
Low refrigerant charge increasing compressor workload
Drive board sending incorrect frequency or voltage to the compressor motor

How to Fix It

Turn off the AC and allow the system to rest for 30 minutes.

If the error was triggered by a temporary overload or extreme heat, a rest period may allow normal restart.
Check that you are not running the AC at maximum cooling in extreme outdoor temperatures.

Most Gree units have an outdoor temperature operating limit — running beyond this limit stresses the compressor.
Ensure the outdoor unit coil is clean and airflow is unrestricted.

A dirty outdoor coil forces the compressor to work harder, increasing the load that triggers demagnetisation detection.
Restart the unit and observe whether U1 returns during normal operation or only under heavy load.

U1 only under heavy load suggests an overloaded system; U1 at startup suggests a compressor or drive board fault.
If U1 is recurring, book a service call for refrigerant check and compressor assessment.

A technician can measure the compressor motor current profile to determine if the magnet is genuinely degrading.

When to Call a Professional

Call a technician if U1 occurs regularly or if the unit is over 8 years old. They will measure compressor operating parameters, refrigerant charge, and drive board output. If the compressor permanent magnet has weakened, compressor replacement is the only fix.

Frequently Asked Questions

What does demagnetisation mean in a Gree inverter compressor?

Gree inverter compressors use a permanent magnet motor (BLDC or IPMSM type). Demagnetisation means the rotor magnetic field is weakening or losing its correct angle relative to the drive signal. The drive board detects this and shuts down to prevent compressor damage.

Is U1 a sign my Gree compressor needs replacing?

Not always — a single U1 event can be caused by a temporary overload or extreme conditions. Frequent U1 errors, especially on units over 8 to 10 years old, can indicate genuine compressor magnet degradation. A technician will be able to tell the difference.

Can low refrigerant cause a Gree U1 error?

Yes. Low refrigerant forces the compressor to run faster and harder to achieve the required cooling output. This extra load can trigger demagnetisation protection. A refrigerant top-up and leak repair can resolve U1 in these cases.