4 blinks, 2.5 s OFFMitsubishi Electric · MSZ / MSY / MUZ / MUY GL NA series · Mini Split

Mitsubishi Electric MSZ / MSY / MUZ / MUY GL NA series error code 4 blinks, 2.5 s OFF

Overcurrent, or compressor startup failure

Needs attention soon

Also written as four blinks, 04, overcurrent, startup failure

Quick answer

On Mitsubishi Electric MSZ / MSY / MUZ / MUY GL NA series, 4 blinks, 2.5 s OFF is a fault. It means overcurrent, or compressor startup failure. A first thing to check: A supply voltage that is too low, which makes the compressor draw excessive current.

Applies to: Mitsubishi Electric MSZ / MSY / MUZ / MUY GL NA series; Mitsubishi Electric MR SLIM GL series split codes · Mini Split
Type of code: Fault; Urgency: Needs attention soon
First safe check: Read the inverter LED: eleven blinks is overcurrent, twelve is the startup failure. That single number separates the two.

Checked 2026-09-26

What 4 blinks, 2.5 s OFF means on this model

An outdoor fault, split by the inverter LED. Eleven LED blinks is a large current flowing into the power module on the smaller models or the IGBT module on the GL24. Twelve LED blinks is a compressor synchronous abnormality, which the manual also calls the compressor startup failure protection, where the compressor current waveform is distorted.

Symptoms you will notice

Upper lamp blinks four times after a three second hold, no beep
The system will not start, or starts and drops out
The system may restart after a delay and trip again
The compressor does not establish a steady hum

Common causes

The code tells you what the control detected, not which part failed. These are the causes we see most often, roughly in order of likelihood:

A supply voltage that is too low, which makes the compressor draw excessive current
A supply voltage that is too high or unstable
A hard to start or failing compressor
A compressor connector that is loose or not seated
A failed power module or IGBT module
A closed stop valve forcing the compressor against a restriction

What you can safely check

These are homeowner-level checks. None of them need you to open a live electrical compartment or work on gas.

Read the inverter LED: eleven blinks is overcurrent, twelve is the startup failure. That single number separates the two.
Measure the supply voltage at the outdoor unit under load. A supply that looks fine at no load is the classic cause of both of these.
Reconnect the compressor connector and check the stop valve, in the order the manual gives.

Do not do these

×Do not keep restarting. Both of these are drive protections and repeated attempts damage the drive section as well as the compressor.
×Do not replace the compressor and the inverter board together without proving which failed, which is an expensive way to fix one fault.
×Do not install heavier fusing to stop the protection operating.

When to call a technician

Book a technician, do not keep resetting it

This fault will not clear on its own. Every power cycle gives the control one more failed attempt, and repeated attempts are what turn a cheap part replacement into a seized or contaminated system.

The refrigerant circuit is sealed and legally requires licensed handling. Opening it without certification releases refrigerant and can put the whole system in violation of regulation, so a low-pressure or high-pressure fault on this equipment is a call-out, not a weekend job.
If the appliance has stopped mid-cycle, is making a noise you have not heard before, or smells burnt, stop reading here and call. Those are symptoms of something the fault code does not describe well enough.

A licensed technician job. Supply voltage under load is not a homeowner measurement.

What it costs to fix

Parts

Compressor $1,400 to $3,000. Inverter P.C. board $500 to $1,200. Power or IGBT module $200 to $600.

Labor

Three to six hours depending on whether the cause is electrical or mechanical.

DIY or technician