If your LG air conditioner displays “CH 35,” it indicates a communication error between the indoor and outdoor units. This issue often stems from wiring problems, power fluctuations, or faulty components, but can usually be resolved with basic troubleshooting or professional help.

Key Takeaways

• CH 35 is a communication error code: It means the indoor and outdoor units of your LG AC are not communicating properly.
• Common causes include wiring issues: Loose, damaged, or corroded wires between units can trigger this error.
• Power supply problems may be involved: Voltage fluctuations or unstable power can disrupt communication signals.
• Outdoor unit malfunctions are possible: Faulty PCB, sensors, or capacitors in the outdoor unit can cause CH 35.
• Resetting the system may help: A power cycle or hard reset can sometimes clear temporary glitches.
• Professional diagnosis is recommended: If basic fixes don’t work, an HVAC technician should inspect the system.
• Regular maintenance prevents errors: Cleaning filters and checking connections can reduce the risk of CH 35.

Quick Answers to Common Questions

What does CH 35 mean on an LG air conditioner?

CH 35 indicates a communication error between the indoor and outdoor units. It means the two parts aren’t exchanging data properly.

Can I fix CH 35 myself?

Yes, in many cases. Try power cycling, checking wiring, and inspecting connections. If the problem persists, call a technician.

Is CH 35 a serious problem?

It can be if ignored. While often fixable, it may lead to system shutdown or reduced efficiency if left unresolved.

Why does my LG AC show CH 35 after a storm?

Power surges or lightning strikes can disrupt communication signals or damage electrical components, triggering the error.

How much does it cost to fix CH 35?

Costs vary. Simple fixes are free; PCB replacement can cost $200–$500. Labor fees depend on your location and technician.

Understanding the CH 35 Error Code on LG Air Conditioners

So, you’re enjoying a hot summer day, and suddenly your LG air conditioner stops cooling. You glance at the display panel and see “CH 35” flashing. Your first thought? “What in the world does that mean?” Don’t panic—this error code is more common than you might think, and in most cases, it’s fixable.

The CH 35 error on an LG air conditioner is a diagnostic code that signals a communication breakdown between the indoor and outdoor units. Think of your AC system like a team: the indoor unit handles air circulation and temperature control, while the outdoor unit manages compression and heat exchange. For everything to work smoothly, these two units need to “talk” to each other constantly. When that conversation gets disrupted, the system throws up the CH 35 flag.

This error doesn’t necessarily mean your AC is broken beyond repair. In fact, many homeowners resolve it with simple steps like checking power connections or resetting the system. However, it’s important not to ignore it. Left unresolved, a persistent CH 35 error can lead to reduced efficiency, uneven cooling, or even complete system shutdown. The good news? With a little know-how, you can often get your LG AC back up and running in no time.

What Does CH 35 Specifically Indicate?

Let’s break it down: CH 35 stands for “Communication Error Between Indoor and Outdoor Units.” In technical terms, it means the data signal being sent from one unit to the other isn’t being received correctly. This communication happens over a dedicated wiring harness that connects the two units. If that signal is interrupted—whether due to physical damage, electrical interference, or component failure—the system can’t coordinate its operations.

LG uses a proprietary communication protocol between its indoor and outdoor units. This allows them to share real-time data about temperature, pressure, fan speed, and compressor status. When the indoor unit sends a command (like “cool to 72°F”), the outdoor unit must acknowledge it and respond accordingly. If that handshake fails, the system logs a CH 35 error and often stops functioning to prevent further damage.

It’s worth noting that CH 35 is different from other error codes like CH 29 (refrigerant leak) or CH 42 (fan motor issue). While those relate to specific mechanical or refrigerant problems, CH 35 is purely about communication. That means the issue is likely electrical or signal-based, not a problem with the cooling process itself.

Common Causes of the CH 35 Error

Now that you know what CH 35 means, let’s explore why it happens. There are several potential culprits, ranging from simple fixes to more complex electrical issues. Understanding these causes can help you diagnose the problem faster and decide whether you can handle it yourself or need professional help.

1. Faulty or Loose Wiring Connections

The most common cause of CH 35 is a problem with the communication wiring between the indoor and outdoor units. Over time, wires can become loose, frayed, or corroded—especially if your AC is installed in a humid or outdoor environment. Even a small break in the wire or a poorly connected terminal can disrupt the signal.

For example, if the technician who installed your unit didn’t secure the wiring harness properly, vibrations from the compressor or fan could gradually loosen the connections. Similarly, rodents or pests might chew through wires, causing intermittent or complete signal loss.

2. Power Supply Issues

Unstable or fluctuating power can also trigger CH 35. If your home experiences frequent voltage spikes, brownouts, or inconsistent electricity, the communication circuit may fail to maintain a stable connection. This is especially true in areas with older electrical grids or during storms.

Additionally, if the outdoor unit isn’t receiving consistent power—due to a tripped breaker, faulty disconnect switch, or damaged wiring—it may not be able to respond to the indoor unit’s signals. Even a momentary power dip can cause the system to lose sync and display the error.

3. Damaged or Faulty PCB (Printed Circuit Board)

The PCB in either the indoor or outdoor unit acts as the “brain” of the system. If the outdoor unit’s PCB is damaged—due to moisture, overheating, or electrical surges—it may fail to process incoming signals correctly. This can result in a CH 35 error, even if the wiring is intact.

Similarly, a malfunctioning indoor PCB might send corrupted or incomplete data, causing the outdoor unit to reject the communication. PCBs are sensitive components, and even minor damage can lead to big problems.

4. Sensor Malfunctions

Some LG models use sensors to monitor communication integrity. If a sensor detects an anomaly—such as a signal delay or voltage drop—it may trigger CH 35 as a protective measure. While the sensor itself might be working fine, it could be reacting to an underlying issue like a failing capacitor or loose connection.

5. Environmental Factors

Extreme weather conditions can also play a role. For instance, heavy rain or snow might seep into the outdoor unit’s electrical compartment, causing short circuits or corrosion. Similarly, excessive heat can cause components to overheat and malfunction, disrupting communication.

How to Troubleshoot the CH 35 Error

Before calling a technician, there are several steps you can take to troubleshoot the CH 35 error. Many of these are simple and safe for homeowners to perform. However, always prioritize safety—turn off power to the unit before inspecting any electrical components.

Step 1: Power Cycle the System

Start with the easiest fix: a full power reset. Turn off the air conditioner at the thermostat, then switch off the circuit breaker that powers the outdoor unit. Wait at least 5–10 minutes to allow any residual electricity to dissipate. This gives the system’s capacitors time to discharge and resets the communication protocol.

After waiting, turn the breaker back on and restart the AC. In some cases, this simple reset clears temporary glitches and restores normal operation. If the CH 35 error disappears, your problem may have been a one-time communication hiccup.

Step 2: Check the Wiring Connections

Next, inspect the wiring between the indoor and outdoor units. Locate the communication wires—usually a set of two or three thin wires running through the wall or conduit. Check for:
– Loose or disconnected terminals
– Frayed or broken insulation
– Signs of corrosion or burn marks
– Chew marks from pests

If you find any damage, you may need to repair or replace the wires. For loose connections, carefully tighten the terminals using a screwdriver. Be sure to match the wire colors to the correct terminals to avoid reversing the signal.

Step 3: Inspect the Outdoor Unit

Open the outdoor unit’s access panel (after turning off power) and look for visible signs of damage. Check the PCB for burnt spots, swollen capacitors, or melted components. Also, ensure the unit is clean and free of debris, as dirt and leaves can cause overheating.

If you notice water inside the compartment, it could indicate a seal failure or drainage issue. Moisture is a major enemy of electrical components and can lead to short circuits.

Step 4: Test the Power Supply

Use a multimeter to check the voltage at the outdoor unit’s disconnect switch. It should match the rated voltage on the unit’s nameplate (usually 208V or 230V). If the voltage is too low or fluctuating, contact your utility provider or an electrician to investigate.

Also, verify that the breaker isn’t tripping repeatedly. A faulty breaker or undersized circuit can cause power instability.

Step 5: Reset the Indoor Unit

Some LG models allow you to reset the indoor unit via the remote or control panel. Refer to your user manual for specific instructions. This can sometimes clear stored error codes and restore communication.

When to Call a Professional

While many CH 35 issues can be resolved with DIY troubleshooting, there are times when you should call a licensed HVAC technician. If you’ve tried the steps above and the error persists, it’s likely a more serious problem.

Signs You Need Professional Help

– The error returns immediately after resetting
– You notice burnt smells or smoke from the unit
– The outdoor unit makes unusual noises (buzzing, clicking, or grinding)
– There’s visible damage to the PCB or wiring
– You’re uncomfortable working with electrical components

A qualified technician has the tools and expertise to perform advanced diagnostics, such as checking signal integrity with an oscilloscope or testing individual components. They can also safely replace faulty PCBs, capacitors, or wiring harnesses.

What to Expect During a Service Call

When the technician arrives, they’ll likely start by scanning the system for error codes and reviewing the service history. They’ll then inspect the wiring, test the power supply, and examine both the indoor and outdoor units.

If the issue is a faulty PCB, they may recommend replacement. While this can be costly (typically $200–$500 depending on the model), it’s often necessary to restore full functionality. In some cases, the entire outdoor unit may need replacement if multiple components are damaged.

Preventing Future CH 35 Errors

Once you’ve resolved the CH 35 error, it’s important to take steps to prevent it from happening again. Regular maintenance and proactive care can go a long way in keeping your LG air conditioner running smoothly.

Schedule Annual Maintenance

Have a professional inspect and service your AC system at least once a year, ideally before the cooling season begins. During this visit, they’ll clean coils, check refrigerant levels, tighten electrical connections, and test communication signals.

Keep the Outdoor Unit Clean

Remove leaves, dirt, and debris from around the outdoor unit. Trim back vegetation to ensure at least 2 feet of clearance on all sides. This improves airflow and reduces the risk of overheating.

Protect Against Power Surges

Install a whole-house surge protector to safeguard your AC and other electronics from voltage spikes. This is especially important in areas prone to lightning or grid instability.

Inspect Wiring Periodically

Every few months, visually inspect the communication wires for signs of wear or damage. If you notice anything unusual, address it promptly.

Use a Stable Power Source

Avoid running high-power appliances (like space heaters or power tools) on the same circuit as your AC. This can cause voltage drops and disrupt communication.

Real-Life Example: Resolving CH 35 at Home

Let’s look at a real-world scenario. Sarah, a homeowner in Florida, noticed her LG AC wasn’t cooling properly. The display showed CH 35, and the outdoor unit was silent. She started by turning off the breaker and waiting 10 minutes before restarting. The error remained.

Next, she inspected the outdoor unit and found a loose wire at the communication terminal. After tightening it and powering the system back on, the error disappeared, and cooling resumed. Sarah’s issue was a simple loose connection—something many homeowners can fix with basic tools.

This example shows that CH 35 doesn’t always mean a major repair. Often, it’s a minor issue that just needs attention.

Conclusion

The CH 35 error on your LG air conditioner might sound alarming, but it’s usually a manageable issue. By understanding what it means—a communication breakdown between indoor and outdoor units—you can take informed steps to resolve it. Start with simple fixes like power cycling and checking wiring, and don’t hesitate to call a professional if needed.

Regular maintenance and careful inspection can prevent CH 35 from recurring, ensuring your AC stays efficient and reliable. With the right approach, you can keep your home cool and comfortable, even on the hottest days.

Frequently Asked Questions

Can a dirty air filter cause CH 35?

No, a dirty filter doesn’t directly cause CH 35. However, it can strain the system and contribute to overheating, which may indirectly affect communication.

Will CH 35 damage my air conditioner?

If left unresolved, it can lead to component stress or system failure. Most units shut down safely to prevent damage when CH 35 appears.

How long does it take to fix CH 35?

Simple fixes take 10–30 minutes. Complex repairs, like PCB replacement, may take 1–2 hours or require a follow-up visit.

Can I still use my AC if it shows CH 35?

It’s not recommended. The system may not cool properly, and continued use could worsen the issue or cause further damage.

Does CH 35 affect all LG AC models?

Yes, CH 35 is a standard error code across most LG inverter air conditioners with split-system designs.

What should I do if CH 35 keeps coming back?

Recurring CH 35 suggests an underlying issue like a failing PCB or persistent wiring problem. A professional diagnosis is essential.