Air Conditioner
LG
Updated Jul 22, 2026
LG AC CH27 Error — Inverter Module (IPM) Fault & Fix
CH27
LG · Air ConditionerCH27 means the Intelligent Power Module (IPM) on the outdoor inverter PCB has failed or is…
Quick answer
CH27 means the Intelligent Power Module (IPM) on the outdoor inverter PCB has failed or is overheating.
What CH27 means
The IPM is the core component of the inverter board — it converts DC bus voltage into the variable-frequency AC that drives the compressor motor. CH27 appears when the IPM's internal protection detects a short circuit, overtemperature, or gate-driver fault.
Fix
This is a board-level repair requiring a technician.
What does the CH27 code mean?
CH27 indicates the Intelligent Power Module (IPM) on the outdoor inverter board has detected an internal fault — short circuit, overtemperature, or gate-driver error.
Common causes
- IPM module failure (age, manufacturing defect, or power surge)
- IPM heat sink overtemperature (blocked ventilation, failed heat-sink fan)
- Compressor winding short feeding back into the IPM
- DC bus voltage spike
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How to fix the CH27 error
Power off immediately
The IPM can be damaged further by repeated restarts.
Do not restart
Call a technician.
Technician diagnosis
The tech will test the IPM with a multimeter (checking each IGBT gate for shorts) and test the compressor windings to rule out a feed-back fault.
Replace the inverter PCB or IPM
Some boards have a replaceable IPM module; others require full PCB replacement.
Check heat sink
Ensure the heat-sink fins are clean and any heat-sink fan is working.
Safety first: The inverter board carries lethal DC bus voltage (300V+) even after power is disconnected (capacitor charge). Only a qualified technician should handle it.
Part you may need: Outdoor inverter PCB / IPM module
If only the IPM is replaceable (some models), it is cheaper than a full PCB. Ask the technician.
Frequently asked questions
Can a power surge cause CH27?
Yes — a voltage spike can destroy the IPM. Install a surge protector on the AC circuit.
Is the compressor still good?
Usually yes — CH27 is an inverter-board fault. The compressor is tested separately.
✎ 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.
