LG Window AC CH01 Error Code — Thermistor Fault Fix

When your LG window air conditioner flashes CH01 on the display, the unit is telling you the room temperature sensor (a thermistor) has failed. AC units need a working temperature sensor to know when to turn the compressor on and off. Without it, the unit either runs nonstop, won’t run at all, or throws the CH01 code.

The good news: this is a cheap and easy fix. A thermistor costs around $10–$20 and takes about 20 minutes to swap. Here’s exactly how to do it.

Quick Reference

Fix 1: Power Cycle the Unit

Before opening anything, a full power cycle can clear a false CH01 code. This is worth trying first.

1. Unplug the AC unit from the wall.
2. Wait 10 minutes (longer for window units — the capacitors need more time to fully discharge).
3. Press and hold the Power button for 10 seconds while unplugged to drain residual charge.
4. Plug the unit back in and turn it on.
5. Set the mode to Cool at 72°F and wait 20 minutes to see if the code returns.

If CH01 comes back, the sensor is genuinely bad. Move to Fix 2.

Fix 2: Inspect the Sensor Wiring

The room temperature sensor is a small thermistor bead located behind the front grille of the unit. Before testing, check the wiring for obvious damage.

1. Unplug the AC.
2. Remove the front grille — usually held by 2–4 screws. Set the screws somewhere safe.
3. Locate the thermistor — look for a small bead or disk about the size of a pea attached to two wires, typically positioned near the air intake. It’s often clipped onto the evaporator coil fins or mounted to a plastic bracket near the top front of the unit.
4. Inspect the wires — check for cuts, fraying, or disconnected wire connectors. A wire that got pinched during installation is a common culprit.
5. Check the connector — trace the wires to where they plug into the control board. Make sure the connector is fully seated.

If you find a damaged wire, you can splice it with wire connectors or replace the entire sensor.

Fix 3: Test the Thermistor with a Multimeter

Now you need to confirm the sensor itself is bad. Grab a multimeter.

1. Unplug the AC (I know — safety first).
2. Disconnect the thermistor from the control board (unplug the two-pin connector).
3. Set your multimeter to ohms (Ω) — the 20k or auto-range setting works best.
4. Touch the probes to the two terminals on the thermistor connector.

What you should see at room temperature (around 70–77°F):

• Room temp thermistor (~77°F): approximately 10,000 ohms (10kΩ)
• If colder (50°F): higher resistance, roughly 20kΩ
• If warmer (90°F): lower resistance, roughly 5kΩ

The relationship is inverse — as temperature goes up, resistance goes down. If the reading is OL (open loop), 0Ω, or any value that doesn’t change when you warm the bead with your fingers (temperature coefficient test), the thermistor is bad.

Note: Some LG window ACs use a different thermistor value (5kΩ or 15kΩ at room temp). If you get a stable reading but are unsure, check your model number against the service manual. A value that doesn’t respond to temperature changes is the real giveaway.

Fix 4: Replace the Thermistor Sensor

If the thermistor tested bad, replacement is straightforward.

1. Order a compatible thermistor. You can use a universal LG window AC thermistor replacement. Make sure the resistance range matches your unit (10kΩ is the most common).
2. Unplug the AC.
3. Remove the front grille (already off if you followed along).
4. Unclip or unscrew the old thermistor from its mounting position.
5. Disconnect the wire harness from the control board.
6. Route the new thermistor wire through the same path and plug it in.
7. Clip the new sensor into the same position — it needs to be exposed to the return air, not touching the metal coil.
8. Reinstall the grille.
9. Plug in the unit and test.

Set the AC to Cool and let it run for 20 minutes. If the compressor kicks on and the room cools down, you fixed it.

Fix 5: Replace the Control Board (Last Resort)

If CH01 persists after replacing the thermistor, the control board itself may have a bad sensor circuit. This is less common but possible.

1. Find a compatible universal AC control board or an LG-specific replacement for your model.
2. Unplug the unit and remove the control panel housing.
3. Unplug every connector (take photos first for reference).
4. Swap in the new board and reconnect everything.
5. Test the unit.

Board replacements on window ACs are usually only worth it on larger units (10,000+ BTU). On a small unit, buying a new AC may be cheaper.

Parts You Might Need

• LG compatible room thermistor (10kΩ)
• Digital multimeter
• Wire connectors for splices
• Universal AC control board

Why This Code Is Usually an Easy Fix

The CH01 code is one of the simpler AC error codes because the room thermistor is a standalone component — easy to access, easy to test, and cheap to replace. Unlike codes related to the compressor or refrigerant charge, there’s no special equipment needed. If you own a multimeter and can turn a screwdriver, you can handle this one.

Related Guides

• LG Window AC Error Codes — Complete Guide
• LG Window AC CH05 Error Code — Condenser Thermistor Fault
• All LG Appliance Resources