AC error codes explained: LG, Daikin, Mitsubishi and Samsung
A code on the display or a pattern of flashing lights is the system telling you exactly what's wrong. Here are the codes we see most often on UK domestic units, in plain English.
LG (DualCool and Standard Plus)
| Code | Meaning | Serious? |
|---|---|---|
| CH01 / 01 | Indoor room sensor fault | Engineer — cheap part |
| CH05 / 05 | Communication error indoor to outdoor | Engineer — often wiring or a tripped outdoor supply |
| CH06 / 06 | Indoor pipe sensor fault | Engineer |
| CH10 | Indoor fan motor locked | Engineer — stop running it |
| CH21 | Outdoor compressor overcurrent | Engineer urgently |
| CH22 | High current on the compressor | Engineer urgently |
| CH38 / CH53 | Refrigerant / communication issue | Engineer — likely a leak |
Daikin
| Code | Meaning | Serious? |
|---|---|---|
| U0 | Refrigerant shortage — you have a leak | Engineer — don't keep running |
| U4 / UF | Indoor–outdoor communication fault | Engineer |
| E5 / E6 | Compressor motor lock / overload | Engineer urgently |
| A5 | Freeze-up protection triggered | Often dirty filters — clean first |
| A6 | Indoor fan motor fault | Engineer |
| H6 | Position detection fault | Engineer |
Mitsubishi Electric
| Code | Meaning | Serious? |
|---|---|---|
| P8 | Pipe temperature abnormal — usually low gas | Engineer |
| E6 / E7 | Indoor–outdoor signal error | Engineer |
| P4 | Drain sensor / float switch triggered | Blocked drain — engineer |
| P5 | Drain pump fault | Engineer |
| U2 | Abnormally high discharge temperature | Engineer urgently |
| F3 / F5 | Fan motor fault | Engineer |
Samsung
| Code | Meaning | Serious? |
|---|---|---|
| E101 / E102 | Communication error indoor to outdoor | Engineer |
| E121 | Indoor room temperature sensor | Engineer |
| E154 | Indoor fan error | Engineer |
| E458 | Outdoor fan error | Engineer |
| E464 | Compressor overcurrent | Engineer urgently |
The two things worth trying before you call
- Power cycle: switch the system off at the isolator (usually a small switch by the outdoor unit or in the loft) for five minutes, then back on. Clears one-off comms glitches.
- Clean the filters and check nothing is blocking the outdoor unit. Freeze-protection and airflow codes often clear straight after.
If the code returns within an hour, it's a genuine fault. Repeatedly resetting a compressor or refrigerant fault is the fastest way to turn a £200 repair into a £1,500 one.
Codes that mean you have a refrigerant leak
Daikin U0, LG CH38, Mitsubishi P8 and anything referencing low pressure all point the same way: gas has escaped. Refrigerant doesn't get used up — if it's low, there's a leak, and topping it up without finding the leak is both illegal under F-Gas regulations and a waste of your money. A proper repair means a nitrogen pressure test, leak locate, repair, vacuum and recharge.
FAQ
Can I reset my air conditioning myself?
Yes — isolate the power for five minutes and restore it. If the same code returns quickly, stop and get it diagnosed rather than resetting repeatedly.
What does error CH05 mean on an LG air conditioner?
A communication failure between the indoor and outdoor unit — usually an interconnecting cable fault, a tripped outdoor supply or a failed PCB. It needs an engineer.
Does an error code mean the unit is scrap?
Rarely. Sensors, fan motors and PCBs are all replaceable parts. Only a seized compressor on an older system usually makes replacement the better call.
Do you repair brands you didn't install?
Yes — we repair and service any domestic brand across the West Midlands, whoever fitted it.
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