Error code CH 05 on your LG air conditioner indicates a communication issue between the indoor and outdoor units. This guide walks you through simple fixes like checking wiring, cleaning components, and resetting the system to get your AC running smoothly again.

Key Takeaways

• CH 05 means a communication failure: The indoor and outdoor units aren’t talking properly, often due to wiring or power issues.
• Check the wiring connections first: Loose, damaged, or corroded wires are the most common cause of this error.
• Clean the control board and connectors: Dust and debris can interfere with signal transmission between units.
• Reset the system after repairs: A power cycle helps the AC recognize restored connections.
• Inspect the outdoor unit’s fan and capacitor: A faulty fan motor or capacitor can disrupt communication.
• Use a multimeter for testing: This tool helps verify voltage and continuity in wires and components.
• Call a technician if problems persist: Internal board failures may require professional repair or replacement.

How to Fix LG Air Conditioner Error Code CH 05

If your LG air conditioner suddenly stops cooling and displays the error code CH 05, don’t panic. This common issue usually means there’s a communication breakdown between the indoor and outdoor units. The good news? In most cases, you can fix it yourself with a few simple steps.

In this guide, you’ll learn exactly what CH 05 means, why it happens, and how to resolve it safely and effectively. We’ll walk you through checking wiring, cleaning key components, testing electrical connections, and when to call a professional. By the end, you’ll have your AC back up and running—without unnecessary repair costs.

Let’s dive in.

What Does Error Code CH 05 Mean?

The CH 05 error code on LG air conditioners stands for “Communication Error Between Indoor and Outdoor Units.” In simpler terms, the indoor unit (the one inside your home) and the outdoor unit (the compressor unit outside) aren’t exchanging signals properly.

These two units rely on a constant flow of data to coordinate cooling, fan speed, and temperature settings. When that connection is interrupted, the system shuts down as a safety measure and displays CH 05.

This error doesn’t mean your AC is broken forever—it’s often a fixable issue related to wiring, power, or dirt buildup. But ignoring it can lead to bigger problems, like compressor damage or complete system failure.

Common Causes of CH 05

Understanding the root cause helps you fix the problem faster. Here are the most common reasons for CH 05:

• Loose or disconnected wiring: Vibration over time can loosen connections between units.
• Damaged or frayed wires: Rodents, weather, or wear can damage the communication cables.
• Corroded connectors: Moisture can cause rust on electrical terminals, blocking signals.
• Dirty control board or sensors: Dust and grime can interfere with electronic communication.
• Faulty outdoor unit fan or capacitor: If the outdoor fan isn’t running, the system may stop communicating.
• Power supply issues: Voltage fluctuations or tripped breakers can disrupt signals.
• Failed control board: In rare cases, the indoor or outdoor PCB (printed circuit board) may be damaged.

Now that you know what might be causing CH 05, let’s get to the fixes.

Step 1: Turn Off the Power

Before doing anything, safety comes first. Working with electrical components can be dangerous if the power is on.

How to Safely Power Down Your AC

1. Go to your home’s main electrical panel (breaker box).
2. Locate the breaker labeled “Air Conditioner” or “HVAC.”
3. Switch it to the OFF position.
4. Wait at least 5 minutes to ensure all capacitors discharge.
5. Optional: Use a non-contact voltage tester to confirm no power is reaching the unit.

Never skip this step. Even if the AC appears off, residual power can cause shocks or damage components.

Step 2: Inspect the Wiring Connections

Most CH 05 errors are caused by wiring problems. The communication between indoor and outdoor units runs through a bundle of wires, usually housed in a conduit.

Locate the Wiring Harness

The wires connecting the indoor and outdoor units typically run through a hole in the wall. Look for a gray or white plastic conduit near the indoor unit. Follow it outside to where it connects to the outdoor unit.

Check for Loose or Disconnected Wires

1. Open the access panel on the indoor unit (usually held by screws).
2. Find the wiring terminal block—this is where the communication wires connect.
3. Check each wire: Are they tightly secured? Are any loose or hanging?
4. Look for signs of burn marks, melted insulation, or discoloration.
5. Repeat the same inspection on the outdoor unit’s terminal block.

If you find loose wires, gently push them back into place and tighten the terminal screws. Use a screwdriver, but don’t overtighten—this can strip the screws or damage the terminals.

Look for Damaged or Frayed Wires

Inspect the entire length of the wire bundle for:

• Chewed or gnawed insulation (common with rodents)
• Cracked or brittle wires (due to sun exposure or age)
• Exposed copper strands

If you see damage, the wire may need to be repaired or replaced. For minor damage, you can use electrical tape as a temporary fix—but plan to replace the wire soon.

Step 3: Clean the Connectors and Control Board

Dust, dirt, and corrosion can block electrical signals. Cleaning the connectors and control board often resolves CH 05.

Clean the Terminal Blocks

1. Use a dry cloth to wipe away dust from the terminal blocks on both indoor and outdoor units.
2. For stubborn grime, use a soft-bristled brush (like an old toothbrush).
3. If you see green or white corrosion (signs of moisture), gently scrub with a cotton swab dipped in isopropyl alcohol.
4. Let everything dry completely before reassembling.

Avoid using water or spray cleaners—moisture can cause short circuits.

Clean the Indoor Unit’s Control Board

The control board (PCB) is the “brain” of your AC. Dust buildup can interfere with signal processing.

1. Locate the control board inside the indoor unit (usually behind the front panel).
2. Use compressed air to blow away dust from the board and connectors.
3. Wipe gently with a dry microfiber cloth.
4. Check for burnt components, swollen capacitors, or discolored areas—these may indicate a failed board.

If the board looks damaged, it may need professional repair or replacement.

Step 4: Check the Outdoor Unit’s Fan and Capacitor

The outdoor unit’s fan helps dissipate heat and maintain proper communication. If it’s not working, the system may shut down with CH 05.

Inspect the Fan Motor

1. Remove the top panel of the outdoor unit (usually held by screws).
2. Look at the fan blade: Is it spinning freely? Or is it stuck?
3. Gently try to spin the fan by hand. It should turn smoothly.
4. If it’s stiff or won’t move, the motor may be seized or the bearings worn out.

A seized fan motor often requires replacement. But first, check the capacitor.

Test the Capacitor

The capacitor gives the fan motor a boost to start spinning. A faulty capacitor is a common cause of fan failure.

1. Locate the capacitor—it’s a small, cylindrical component near the fan motor.
2. Look for bulging, leaking, or burnt marks—these are signs of failure.
3. Use a multimeter to test capacitance (if you’re comfortable with electronics).
4. If the reading is far below the labeled value (e.g., 5µF reading as 1µF), replace the capacitor.

Replacing a capacitor is relatively easy and inexpensive. Buy a compatible one from an HVAC supplier or online.

Step 5: Reset the Air Conditioner

After making repairs, a system reset helps the AC recognize the restored connections.

How to Reset Your LG AC

1. Turn the breaker back ON.
2. Wait 2–3 minutes for the system to power up.
3. Use the remote to turn on the AC.
4. Set it to Cool mode and a low temperature (e.g., 68°F).
5. Listen for the outdoor unit to start within 5–10 minutes.

If the CH 05 error returns immediately, the problem may not be fully resolved.

Alternative Reset Method

Some LG models allow a soft reset via the remote:

1. Press and hold the Power button for 5–10 seconds.
2. The display should blink, then reset.
3. Try turning the AC on again.

This doesn’t replace a full power cycle but can help clear minor glitches.

Step 6: Test the System

Once the AC is back on, monitor it closely.

What to Watch For

• Does the outdoor unit start within 5–10 minutes?
• Is cool air coming from the vents?
• Does the error code reappear?
• Are there unusual noises (clicking, buzzing, grinding)?

If everything works normally for 30 minutes, the CH 05 error is likely fixed.

But if the error returns, move to advanced troubleshooting.

Advanced Troubleshooting for CH 05

If the basic steps didn’t work, the issue may be more complex.

Use a Multimeter to Test Voltage

A multimeter helps you check if power is reaching the outdoor unit.

1. Set the multimeter to AC voltage (usually 200V or 250V range).
2. Turn the breaker ON.
3. At the outdoor unit’s terminal block, test between the L (live) and N (neutral) terminals.
4. You should see 220–240V (in most homes).
5. If voltage is low or zero, there may be a wiring issue in your home’s electrical system.

Low voltage can prevent the outdoor unit from communicating properly.

Check for Grounding Issues

Poor grounding can disrupt signals.

1. Ensure the outdoor unit is properly grounded.
2. Look for a green or bare copper wire connected to the unit’s chassis.
3. Use a multimeter to test continuity between the ground terminal and the unit’s metal frame.
4. If there’s no continuity, the grounding may be faulty.

Consult an electrician if grounding issues are suspected.

Inspect the Communication Wires

The communication between units uses low-voltage wires (usually 24V). These can be damaged or shorted.

1. Disconnect the communication wires at both ends.
2. Use a multimeter to test for continuity between the two wires.
3. There should be no short (infinite resistance) between them.
4. If the wires are shorted or open (no continuity), they may need replacement.

Replacing communication wires is a job for a technician unless you’re experienced with HVAC systems.

When to Call a Professional

While many CH 05 errors can be fixed at home, some issues require expert help.

Signs You Need a Technician

• The error returns after multiple resets and repairs.
• You find burnt components or a damaged control board.
• The outdoor unit still doesn’t power on.
• You’re uncomfortable working with electrical systems.
• The warranty is still active—DIY repairs may void it.

A certified HVAC technician can perform advanced diagnostics, replace internal boards, and ensure safe operation.

Preventing CH 05 in the Future

Once your AC is fixed, take steps to avoid CH 05 from happening again.

Regular Maintenance Tips

• Clean filters monthly: Dirty filters reduce airflow and strain the system.
• Inspect wiring annually: Check for loose or damaged wires before summer.
• Keep the outdoor unit clean: Remove leaves, dirt, and debris from around the unit.
• Schedule professional tune-ups: Have a technician service your AC every 1–2 years.
• Protect from pests: Use wire mesh to prevent rodents from chewing cables.

Prevention saves time, money, and frustration.

Conclusion

The LG air conditioner error code CH 05 can be frustrating, but it’s often fixable with basic troubleshooting. By checking wiring, cleaning components, and resetting the system, you can restore communication between the indoor and outdoor units.

Start with safety—always turn off the power. Then inspect connections, clean terminals, and test the fan and capacitor. If the error persists, use a multimeter or call a professional.

With regular maintenance, you can prevent CH 05 and keep your AC running smoothly for years. Don’t let a simple error code leave you sweating—take action today and enjoy cool, comfortable air again.