Air Conditioner
LG
Updated Jul 21, 2026
LG AC CH25 Error — Incoming Power Supply Fault & Fix
CH25
LG · Air ConditionerCH25 means the outdoor unit has detected an incoming power supply error — voltage is outsi…
Quick answer
CH25 means the outdoor unit has detected an incoming power supply error — voltage is outside the acceptable range or phase is missing.
What CH25 means
The outdoor inverter board monitors the incoming mains voltage. CH25 appears when the voltage drops below or rises above the acceptable operating range (typically 180V-260V for single-phase units), or when a phase is missing on three-phase commercial units.
How to fix it
What does the CH25 code mean?
CH25 indicates an incoming power supply error on the outdoor unit. Mains voltage is outside the safe operating range or a phase is missing.
Common causes
- Low mains voltage (brownout, undersized cable)
- High mains voltage (supply above 260V)
- Missing phase (three-phase units)
- Loose mains terminal connection on the outdoor unit
- Faulty circuit breaker or contactor
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How to fix the CH25 error
Check mains voltage
Measure at the outdoor unit disconnect with a multimeter. Single-phase should be 200-240V (nominal).
Tighten terminals
Open the outdoor terminal block and ensure all connections are secure.
Check the breaker
Ensure it is fully on and not tripping.
Install a voltage stabiliser
If your area has chronic voltage issues, a stabiliser protects the inverter.
For three-phase units, check all phases
Use a phase-sequence meter to confirm correct phase order.
Safety first: Mains voltage is lethal. Only a qualified electrician should diagnose power supply issues.
Part you may need: Voltage stabiliser / mains wiring
In Bangladesh and South Asia, voltage instability is a leading cause of CH25. A stabiliser rated for your AC's power consumption is a worthwhile investment.
Frequently asked questions
Can a generator cause CH25?
Yes — generators with poor voltage regulation often trigger CH25. Use an inverter generator or a stabiliser between the generator and the AC.
Will CH25 damage my AC?
The error itself protects the AC by stopping it. Repeated exposure to voltage extremes can degrade the inverter board over time.
✎ Written by
REZAUL Karim (Riad)
REZAUL Karim (Riad) is the founder of ErrFixHub and a hands-on electronics and home-appliance repair specialist with over 15 years of experience diagnosing and fixing air conditioners, washing machines, refrigerators, inverters and other household appliances. He built ErrFixHub to turn cryptic error codes into clear, step-by-step fixes anyone can follow — cross-checking every code against manufacturer documentation and real repair-bench experience.
