LG Mini-Split CH26 Error Code — CT Sensor Fault
Error Code CH26 on LG mini-split and multi-zone systems indicates a current transformer (CT) sensor fault on the outdoor unit. The CT sensor monitors the compressor current draw and is critical for inverter compressor protection. When the sensor fails or reads outside its expected range, CH26 is triggered.
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What Is the CT Sensor?
The CT (current transformer) sensor is a small toroidal coil that clamps around the compressor supply wire. It measures compressor current without direct electrical contact. The outdoor PCB reads this signal to protect the compressor from overcurrent and to control inverter frequency.
Common Causes {#most-likely-cause}
| Cause | Likelihood |
|---|---|
| CT sensor failed or disconnected | Very High |
| CT sensor wiring harness loose or broken | High |
| Outdoor PCB analog input failure | Medium |
| CT sensor mounted incorrectly (not around wire) | Medium |
| Actual compressor overcurrent (compressor fault) | Low |
Step-by-Step Diagnosis {#diagnosis}
Step 1 — Locate the CT sensor
- The CT sensor is inside the outdoor unit electrical compartment
- It is a small ring or clamp around the compressor power wire (typically the black wire on single-phase units)
- Visually confirm it is seated properly and the wire passes through the center of the ring
Step 2 — Check the connector
- The CT sensor connects to the outdoor PCB via a small 2-pin connector
- Disconnect and re-seat the connector firmly
- Inspect the connector for corrosion or bent pins
Step 3 — Measure CT sensor output
- The CT sensor outputs a small AC voltage proportional to current
- With unit running and a clamp meter on the output leads: verify millivolt-range AC signal
- If no signal while compressor is running: sensor is open — replace
Step 4 — Check wiring
- Trace the CT sensor wiring back to the outdoor PCB
- Look for pinched, cut, or melted wire insulation near sheet metal edges
- Check for condensate dripping on the connector causing corrosion
Step 5 — Verify compressor operation
- If the CT sensor and wiring are good, the board analog input may have failed
- Check for other related faults: compressor overcurrent codes, inverter faults
- If compressor is actually overloaded, fix the root cause (refrigerant, voltage)
Replacement Parts {#parts}
| Part | Notes |
|---|---|
| CT sensor (current transformer) | LG OEM part — match model number |
| Outdoor PCB | Only replace after confirming sensor and wiring are good |
Need Replacement Parts?
Finding the right replacement parts for your equipment is critical to getting it running again. Check current prices on Amazon — prices and availability change frequently.
Reset Procedure
- Repair or replace the CT sensor
- Confirm connector is fully seated
- Restore power and attempt restart
- CH26 clears automatically on a successful startup if the sensor reads correctly
Note: LG CH26 is sometimes confused with CH25 (compressor overcurrent). CH25 means the compressor actually drew too much current; CH26 means the measurement circuit itself has failed. The repair procedures are different — CH25 leads to the compressor, CH26 leads to the sensor.