Title: How to Replace Thermistor in Lg Air Conditioner
Replacing a thermistor in an LG air conditioner can restore proper temperature control and improve efficiency. This guide walks you through diagnosing the issue, safely removing the old part, and installing a new one—no technician needed.
Key Takeaways
Safety first: Always disconnect power before working on your LG AC unit to prevent electric shock or damage.
Identify the right thermistor: LG models use different thermistors (indoor, outdoor, pipe, etc.)—check your model number to get the correct replacement.
Use proper tools: A multimeter, screwdrivers, and needle-nose pliers are essential for accurate testing and installation.
Test before replacing: Confirm the thermistor is faulty using a multimeter to avoid unnecessary part replacement.
Follow disassembly order: Take photos during disassembly to help reassemble the unit correctly.
Seal and secure: Ensure all panels and covers are tightly sealed after replacement to maintain efficiency and prevent dust ingress.
Test the system: Run the AC after installation to verify temperature readings and cooling performance are back to normal.
How to Replace Thermistor in LG Air Conditioner
If your LG air conditioner isn’t cooling properly, turning on and off randomly, or showing error codes like “CH 01” or “CH 02,” the culprit might be a faulty thermistor. The thermistor is a small but critical sensor that monitors temperature and sends data to the AC’s control board. When it fails, your AC can’t regulate temperature correctly, leading to discomfort and higher energy bills.
The good news? Replacing a thermistor in an LG air conditioner is a DIY-friendly task—if you follow the right steps. In this comprehensive 2026 guide, we’ll walk you through everything you need to know: from diagnosing the problem and gathering tools to safely removing the old thermistor and installing a new one. You’ll save hundreds on technician fees and gain confidence in maintaining your home cooling system.
Whether you have a window unit, split system, or ductless mini-split, this guide covers the most common LG models. We’ll focus on indoor unit thermistors, which are the most frequently replaced, but we’ll also touch on outdoor and pipe thermistors where relevant.
Let’s get started—your cooler, more efficient home awaits.
What Is a Thermistor and Why Does It Matter?
Visual guide about How to Replace Thermistor in Lg Air Conditioner
Image source: partsexpert.ca
Diagram showing thermistor location and wiring in an LG indoor unit.
Before diving into the replacement process, it’s important to understand what a thermistor does. A thermistor (short for “thermal resistor”) is a type of temperature sensor that changes its electrical resistance based on temperature. In LG air conditioners, thermistors are used in several locations:
- Indoor air thermistor: Measures the room temperature.
- Outdoor air thermistor: Monitors outside air temperature.
- Pipe thermistor: Tracks the temperature of refrigerant lines.
- Coil thermistor: Monitors the evaporator or condenser coil temperature.
These sensors send real-time temperature data to the AC’s control board, which adjusts compressor speed, fan operation, and refrigerant flow accordingly. If a thermistor fails or gives inaccurate readings, the AC may:
- Fail to turn on
- Cycle on and off too frequently
- Blow warm air instead of cold
- Display error codes
- Overheat or freeze up
In 2026, LG continues to use high-precision NTC (Negative Temperature Coefficient) thermistors in their units. These are reliable but can degrade over time due to moisture, dust, or electrical surges. Replacing a faulty thermistor is often the simplest and most cost-effective fix.
NTC thermistors decrease resistance as temperature rises, which the control board interprets to adjust cooling output. For precise diagnostics, consult the resistance‑temperature table in your model’s service manual. LG’s official support portal provides detailed specifications for each part number. LG support documentation
Signs You Need to Replace the Thermistor
Not every cooling issue is caused by a bad thermistor, so it’s essential to confirm the problem before replacing parts. Here are the most common symptoms of a failing thermistor in an LG air conditioner:
Inconsistent cooling: The AC turns on but doesn’t reach the set temperature, or it cools unevenly.
Frequent cycling: The unit turns on and off every few minutes (short cycling), which can damage the compressor.
Error codes: LG units display specific codes for thermistor issues. Common ones include: CH 01 – Indoor air thermistor error
CH 02 – Outdoor air thermistor error
CH 03 – Pipe thermistor error
CH 04 – Coil thermistor error
Freezing or overheating: The evaporator coil freezes up, or the unit overheats and shuts down.
No response from remote: In some cases, a faulty thermistor can cause communication errors between the remote and the unit.
If you notice any of these signs, it’s time to test the thermistor.
Similar symptoms can also stem from refrigerant leaks, a clogged filter, or condenser problems. If the thermistor tests okay, our guide on diagnosing warm air issues walks through the next checks.
Common LG Thermistor Part Numbers and Compatibility
LG uses several thermistor part numbers across its lineup. Common indoor air thermistors include 6871A20004C, 6871A20004D, and 6871A20004E. Outdoor and pipe sensors often carry numbers like 6871A20005A or 6871A20006B. Always verify the exact part number printed on the old sensor or look it up by model number on LG’s parts site. Using the wrong part can cause persistent error codes or erratic cooling.
Tools and Materials You’ll Need
Before starting, gather the following tools and materials. Having everything ready will make the process smoother and safer.
Multimeter: Essential for testing the thermistor’s resistance. A digital multimeter with ohms (Ω) setting is ideal.
Screwdrivers: Phillips and flathead screwdrivers for removing panels and screws.
Needle-nose pliers: For gently disconnecting wires and clips.
Replacement thermistor: Make sure it matches your LG model. Check the part number on the old thermistor or consult LG’s official parts database.
Electrical tape: For securing loose wires temporarily.
Work gloves: To protect your hands from sharp edges.
Safety glasses: Recommended when working near electrical components.
Flashlight or work light: For better visibility inside the unit.
Camera or smartphone: To take photos during disassembly for easier reassembly.
You can purchase replacement thermistors online from LG’s official store, Amazon, or appliance parts retailers. Prices typically range from $10 to $25, depending on the model.
An antistatic wrist strap and a small tube of dielectric grease for the connector pins are inexpensive additions that protect sensitive electronics. Keeping a maintenance log helps track when sensors were last checked, and following a routine upkeep schedule can prevent repeat failures.
Step 1: Turn Off Power and Prepare the Work Area
Safety is the top priority when working with any electrical appliance. Air conditioners operate on high voltage, and even residual current can be dangerous.
Disconnect Power at the Source
Turn off the AC using the remote or control panel.
Locate the circuit breaker for the air conditioner in your home’s electrical panel.
Switch off the breaker dedicated to the AC unit. If you’re unsure which one it is, turn off the main breaker for the room or area.
For added safety, unplug the unit if it’s a window or portable AC. For split systems, ensure the outdoor unit is also powered down.
Wait Before Proceeding
Allow the unit to sit for at least 10–15 minutes. This gives capacitors time to discharge and reduces the risk of electric shock.
Clear the Work Area
Move furniture, rugs, or obstacles away from the AC unit. Ensure you have enough space to work comfortably. Lay down a clean towel or mat to place screws and parts on.
Step 2: Access the Indoor Unit
The thermistor is usually located inside the indoor unit, near the evaporator coil or air intake. Access varies slightly depending on your LG model, but the general process is similar.
Remove the Front Panel
Locate the front grille or panel of the indoor unit. It’s typically held in place by clips or screws.
Use a screwdriver to remove any visible screws at the bottom or sides.
Gently pull the panel forward. Some models have a hinge at the top—lift and tilt it upward.
Set the panel aside carefully to avoid damaging the plastic clips.
Remove the Air Filter
Once the front panel is off, you’ll see the air filter.
Slide the filter out of its slot.
Clean it with water and let it dry, or replace it if it’s dirty or damaged.
Set it aside—you’ll reinstall it later.
Locate the Thermistor
The indoor air thermistor is usually a small, bead-like sensor mounted on a plastic bracket near the evaporator coil. It’s connected to a thin wire that runs to the control board.
Look for a small white or black component with two wires.
It may be clipped into a plastic holder or taped to a pipe.
Take a photo of the area before disconnecting anything—this will help during reassembly.
Step 3: Test the Thermistor with a Multimeter
Before replacing the thermistor, confirm it’s actually faulty. A working thermistor should show resistance that changes with temperature.
Set Up the Multimeter
Turn the multimeter dial to the ohms (Ω) setting. Use the 20kΩ range for most thermistors.
Touch the red and black probes together to ensure the meter reads zero (or close to it).
Disconnect the Thermistor
Carefully unplug the thermistor’s wire connector from the control board. Use needle-nose pliers if needed.
Do not pull on the wires—grip the connector itself.
Measure Resistance
Touch one probe to each terminal of the thermistor.
At room temperature (around 70°F or 21°C), a typical LG thermistor should read between 5kΩ and 15kΩ.
If the reading is “OL” (open loop) or zero, the thermistor is faulty.
For accuracy, compare your reading to the specifications in your LG service manual (available online).
Optional: Test Temperature Response
To further confirm, warm the thermistor slightly (e.g., with your hand or a hair dryer) and watch the resistance drop. If it doesn’t change, the sensor is dead.
Many service manuals include a resistance‑vs‑temperature chart. At 77 °F (25 °C) a typical LG indoor thermistor reads near 10 kΩ; at 32 °F (0 °C) it rises to roughly 30 kΩ. If your readings fall outside these bands, the sensor is out of spec even if it isn’t open or shorted.
Thermistor Resistance Reference Chart
Below is a quick reference for common LG NTC thermistors (10 kΩ at 25 °C, B‑value 3435 K). Use this as a sanity check; always defer to your specific model’s manual.
| Temp (°F) | Temp (°C) | Approx. Resistance (kΩ) |
|---|---|---|
| 32 | 0 | 30.0 |
| 50 | 10 | 18.5 |
| 68 | 20 | 12.0 |
| 77 | 25 | 10.0 |
| 86 | 30 | 8.3 |
| 104 | 40 | 5.5 |
Print or save this table for fast on‑site verification.
Step 4: Remove the Old Thermistor
Once you’ve confirmed the thermistor is bad, it’s time to remove it.
Detach the Sensor
If the thermistor is clipped into a holder, gently squeeze the clip and pull it out.
If it’s taped to a pipe, carefully peel off the tape. Avoid damaging the pipe or surrounding components.
Note the orientation and position—this matters for reinstallation.
Disconnect the Wires
If the connector is tight, wiggle it gently while pulling.
Label the wires with tape if they’re not color-coded (e.g., “Red to Red,” “White to White”).
Place the old thermistor in a safe spot—you may need it for reference.
Step 5: Install the New Thermistor
Now that the old sensor is out, install the replacement.
Prepare the New Thermistor
Check that the new thermistor matches the old one in size, shape, and wire length.
Ensure the connector type is identical (most LG units use 2-pin JST connectors).
Connect the Wires
Plug the new thermistor into the same connector on the control board.
Push firmly until it clicks into place.
Double-check polarity if the connector is keyed (most are, so it only fits one way).
Secure the Sensor
Clip the new thermistor into the same holder or position it where the old one was.
If it was taped to a pipe, use electrical tape to secure it—don’t use duct tape, as it can degrade.
Ensure the sensor is snug and won’t vibrate loose.
Step 6: Reassemble the Unit
With the new thermistor in place, it’s time to put everything back together.
Reinstall the Air Filter
Slide the clean or new filter back into its slot.
Make sure it’s seated properly and not bent.
Reattach the Front Panel
Align the panel with the unit and press it into place.
Secure any screws you removed earlier.
Ensure all clips are engaged and the panel is flush with the unit.
Double-Check Connections
Before restoring power, verify:
All wires are connected and not pinched.
No tools or debris are left inside the unit.
The thermistor is securely mounted and not touching sharp edges.
Step 7: Restore Power and Test the System
Now it’s time to see if your repair worked.
Turn Power Back On
Go to the circuit breaker and switch the AC breaker back on.
Plug in the unit if it’s a window or portable model.
Test the Air Conditioner
Turn on the AC using the remote.
Set it to cooling mode and choose a low temperature (e.g., 68°F).
Listen for normal startup sounds—compressor, fan, etc.
Check that cool air is blowing within 5–10 minutes.
Use a thermometer to verify the air temperature is dropping.
Monitor for Error Codes
Watch the display for any error codes.
If CH 01 or similar appears, the thermistor may still be faulty or improperly installed.
Recheck connections and resistance if needed.
Troubleshooting Common Issues
Even with careful installation, problems can arise. Here’s how to handle them:
AC Still Not Cooling
- Check the air filter—it may be clogged.
- Ensure the outdoor unit is clean and unobstructed.
- Verify refrigerant levels (requires a technician).
Error Code Persists
- Recheck the thermistor connection.
- Test resistance again—ensure the new part is functional.
- Inspect the control board for damage or burnt components.
Unit Freezes Up
- This could indicate a refrigerant leak or dirty coil—clean the evaporator and check for blockages.
- Ensure the fan is running at full speed.
Thermistor Loose or Vibrating
- Re-secure it with a clip or tape.
- Avoid placing it near moving parts.
If the unit still freezes or shows error codes after verifying the thermistor, the issue may lie with the condenser fan, refrigerant charge, or control board. Our condenser troubleshooting guide covers those deeper diagnostics.
When to Call a Professional
While thermistor replacement is DIY‑friendly, certain situations warrant a certified technician: refrigerant handling (EPA Section 608 certification required), control board replacement, or if the unit is under warranty. Attempting sealed‑system repairs can void the warranty and pose safety risks. A professional can also perform a full system performance test to ensure optimal efficiency. If you're installing a new split system, our split AC installation guide covers the process.
Safety Tips and Best Practices
To ensure a safe and successful repair:
Never work on a live unit—always disconnect power.
Use insulated tools to reduce shock risk.
Keep the work area dry and well-lit.
Don’t force components—if something doesn’t fit, reassess.
When in doubt, consult the LG service manual or contact support.
Regularly cleaning the indoor coil and filter reduces dust buildup that can insulate the thermistor and cause drift. If your system is over 10 years old, consider whether upgrading to a newer, more efficient model makes sense. Our guide on selecting a new unit breaks down the key factors.
Preventive Maintenance to Extend Thermistor Life
Schedule a yearly inspection before cooling season: clean the evaporator coil, check the thermistor’s mounting clip for corrosion, and verify resistance at ambient temperature. Keep the area around the outdoor unit clear of debris to maintain proper airflow. A little preventive care avoids mid‑summer breakdowns and keeps energy bills low. Keep your system running efficiently with our seasonal maintenance checklist.
Conclusion
Replacing a thermistor in your LG air conditioner is a practical and rewarding DIY project that can restore your unit’s performance and save you money. By following this 2026 guide, you’ve learned how to diagnose the issue, test the sensor, and install a replacement safely and correctly.
Remember: always prioritize safety, use the right tools, and double-check your work. With a new thermistor in place, your LG AC should cool efficiently, maintain accurate temperatures, and avoid unnecessary cycling.
If you encounter persistent issues, don’t hesitate to consult a certified technician—but for most thermistor failures, you’ve got this. Enjoy your cool, comfortable home all season long.
Frequently Asked Questions
How do I know which thermistor my LG model needs?
Check the part number printed on the old sensor or look up your model number on LG’s official parts website. The service manual for your specific unit also lists the correct thermistor part numbers.
Can I use a universal thermistor instead of an OEM part?
Universal thermistors may fit electrically but often have different resistance curves, leading to inaccurate temperature readings and error codes. Using the exact OEM part ensures proper communication with the control board.
Why does my AC still show CH 01 after replacing the thermistor?
The error may persist if the connector is loose, the wiring is damaged, or the control board itself is faulty. Re‑verify the resistance of the new sensor and inspect the connector pins for corrosion or bent terminals.
Is it safe to test the thermistor without a multimeter?
No. A multimeter is the only reliable way to measure resistance and confirm the sensor’s health. Guessing based on symptoms can lead to unnecessary part replacement or missed faults.
How often should I check the thermistor as part of maintenance?
Inspect the thermistor’s mounting and clean the surrounding area during your annual pre‑season AC tune‑up. Testing resistance once a year helps catch drift before it causes performance issues.
