Gree Split AC Error Code U3 — What It Means & How to Fix It

What Does This Error Mean?

U3 means the voltage inside the IPM (Intelligent Power Module) is too high for safe operation. This is similar to PH but specifically measured inside the power module itself. Check your mains voltage and call a technician if the error persists.

Affected Models

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

Common Causes

Mains supply voltage too high, pushing DC bus voltage into the IPM danger zone
DC bus capacitor failing and allowing voltage spikes to reach the IPM
Regenerative voltage spike during rapid compressor deceleration
Voltage spike or surge entered the unit during a storm or grid event
IPM module nearing end of life with degraded internal protection

How to Fix It

Turn off the AC and switch off the outdoor circuit breaker.

If U3 was caused by a one-time voltage spike, this clears the fault.
Wait 10 minutes before restoring power — do not rush.

The IPM internal capacitors need time to discharge to safe levels.
Check your mains supply voltage if you have access to a voltmeter.

Voltage consistently above the rated input maximum (around 264V on most Gree units) will cause recurring U3.
Restore power and attempt one restart.

If U3 was a one-off spike event, the unit should start normally.
If U3 returns on restart, call a technician to inspect the capacitor and IPM.

A failing DC bus capacitor is the most common cause of recurring voltage spikes reaching the IPM.

When to Call a Professional

Call a technician if U3 persists after a power cycle and your supply voltage is normal. The IPM holds dangerous voltages even after shutdown. Only a qualified technician should access the drive board compartment.

Frequently Asked Questions

What is the difference between Gree PH and U3 errors?

PH monitors the DC bus voltage at the main bus level. U3 monitors the voltage specifically inside the IPM module. Both indicate over-voltage but U3 is more directly related to IPM component stress.

Can I prevent U3 errors on my Gree AC?

Installing a whole-house surge protector or a dedicated surge protector on the AC circuit helps. This catches grid voltage spikes before they reach the outdoor unit. Regular servicing also helps catch degrading capacitors before they cause U3.

Is U3 a sign the IPM needs replacing?

A single U3 event after a power surge usually does not mean the IPM is failing. If U3 occurs regularly without any apparent external cause, the IPM or the DC bus capacitors are likely degrading. A technician can test both.