R-Pro › Field cases › Air conditioning
LG AC CH Error Code Master — CH01–CH07 Field Diagnosis
Likely causes
Step 1 — CH code meanings and check locations
Check: **CH01** = indoor ROOM temp sensor OPEN/SHORT. Measure NTC resistance (10 kΩ at 25°C typical). **CH02** = indoor inlet pipe sensor OPEN/SHORT. Evaporator inlet area. **CH03** = remote comm fault. Check battery, IR LED, receiver (phone-camera IR test). **CH04** = drain pump fault or drain clogged. Check pump coil resistance, float switch. **CH05** = indoor-outdoor comm fault (most common). Check L/N wiring, termination resistor, 14/4 cable continuity. **CH06** = indoor outlet pipe sensor OPEN/SHORT. Evaporator outlet. **CH07** = multi-zone indoor units in conflicting modes (cool/heat). Tell user to set all to same mode.
What to do: **Sensor faults (CH01/02/06)**: replace with same-spec NTC (matching B-constant). Also check cable continuity. **CH03 remote**: replace battery → IR test → if still bad, replace remote or receiver PCB. **CH04 drain**: clean pump → replace if open / vacuum-suck drain pipe. **CH05 comm**: most common = L and N swapped → fix. If open, replace 14/4 cable. Confirm termination resistor ON. **CH07**: educate user (multi-zone = one outdoor with multiple indoors = must use same mode). After visit: log digital + attach photos.
**Field trick**: 80%+ of CH codes are simple wiring/sensor faults. Major faults (compressor, PCB) are rare. **CH05 comm fault** most common — ~30% of first visits. L/N swap is very common at install (color codes ignored). **CH04 drain** = mold/slime (spikes 3–4 weeks after season starts). **CH07** = user error, fix in 5 min by education. **Same CH code repeating** = consider part replacement.
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