LG Window Air Conditioner Error Codes — Complete Fix Guide
Your LG window air conditioner throws an error code. You need to know what it means and how to fix it. This guide covers every common LG window AC error code with step-by-step repair instructions.
Master Quick Reference
| Code | Meaning | Severity | DIY Fixable? |
|---|---|---|---|
| CH01 | Room temperature sensor (thermistor) fault | Moderate | Yes — sensor replacement |
| CH02 | Evaporator coil temperature sensor fault | Moderate | Yes — sensor replacement |
| CH05 | Condenser coil temperature sensor fault | Moderate | Yes — sensor replacement |
| CH10 | Compressor discharge temperature sensor fault | High | Sometimes — sensor or board |
| CH11 | Communication error between display and main board | High | Check wiring, replace board |
| Lo or Err | Low refrigerant or severe sensor fault | High | Professional service needed |
Parts and Tools You Will Need
- LG thermistor kit (10kΩ) — includes room, evaporator, and condenser sensors (check price on Amazon)
- Digital multimeter with resistance mode (on Amazon)
- Control board compatible with your model (on Amazon)
- Coil cleaning spray (on Amazon)
- Phillips and flathead screwdrivers
- Wire connectors and crimp tool
Fix Walkthroughs
CH01 — Room Temperature Sensor Fault
The room thermistor sits behind the air intake grille. It measures the air temperature coming into the unit so the control board knows when to cycle the compressor.
Step 1: Unplug the AC. Remove the front grille and air filter.
Step 2: Locate the room thermistor. It is a small bead or flat sensor on two wires mounted in the air intake path, usually near the top or side of the unit.
Step 3: Disconnect the thermistor from the control board. Set your multimeter to resistance mode.
Step 4: At room temperature (77°F / 25°C), the sensor should read approximately 10,000 ohms (10kΩ). If it reads open (OL), zero, or far outside range (under 2kΩ or over 100kΩ), replace it.
Step 5: Install the new thermistor in the same position. Connect the wires using butt splices. Route wiring away from the fan blade.
CH02 — Evaporator Coil Sensor Fault
This sensor is embedded in the evaporator coil fins. It monitors the cold coil temperature to prevent freezing.
Full detailed repair steps available in our dedicated CH02 guide.
Quick diagnosis: Unplug, locate sensor on evaporator coil, disconnect from board, test resistance at room temp. Target: 10kΩ. Replace if out of spec.
CH05 — Condenser Coil Sensor Fault
The condenser coil is the hot coil on the back or side of the unit. This sensor monitors its temperature.
Step 1: Unplug the AC. Remove the rear grille and any metal covers protecting the condenser.
Step 2: Locate the condenser thermistor. It clips into the condenser coil fins on the back of the unit. It looks identical to the other thermistors — a small bead with two wires.
Step 3: Disconnect from the board. Test resistance. Expected: 10kΩ at 77°F.
Step 4: Replace with a matching LG thermistor if reading is out of spec. Route the new wires carefully to avoid contact with the hot condenser tubing.
CH10 — Compressor Discharge Sensor Fault
This sensor reads the compressor discharge line temperature. It protects the compressor from overheating.
Step 1: Unplug the AC. Remove the rear access panel to reach the compressor area.
Step 2: The discharge sensor clips onto the compressor discharge tube — the small-diameter copper line leaving the top of the compressor.
Step 3: Disconnect the sensor and test resistance. This sensor is also a 10kΩ thermistor at room temperature.
Step 4: If the sensor tests good (around 10kΩ) but the error persists, the problem is the control board. Inspect the board for burn marks or bulging capacitors.
CH11 — Communication Error
This code means the display board and the main control board are not talking to each other.
Step 1: Unplug the unit. Open the control panel. Check the ribbon cable or wire harness connecting the display board to the main board.
Step 2: Reseat the connectors firmly. Look for bent or broken pins.
Step 3: If the connection looks clean but the code persists, either the display board or the main board has failed. Replace the display board first — it is cheaper and fails more often.
General Maintenance Tips
- Clean the air filter every month during cooling season. A clogged filter causes evaporator coil temperature fluctuations that can trigger CH02 and CH05 codes.
- Clean the condenser coils yearly. Use coil cleaning spray and a garden hose. Dirty coils trap heat and strain the condenser sensor.
- Level the unit. A window AC that is not level can cause condensate to pool on sensors, leading to intermittent error codes.
- Avoid extension cords. Plug the AC directly into a wall outlet. Voltage drop from a long extension cord can cause power-related sensor errors.
When to Call a Professional
Some issues need a licensed HVAC technician:
- CH10 or CH11 codes that do not clear after sensor replacement
- Refrigerant leaks (suspect this if the AC blows warm air but shows no error code at first)
- Compressor failure symptoms (loud humming, tripping breaker, no cooling)
A window AC service call runs $150 to $350. Compare that to the cost of a replacement unit. If your unit is over 8 years old and the control board is bad, replacement is often the better call.