How to troubleshoot an 05 error on an LG multi-split air conditioner

If your LG multi-split air conditioner is displaying a 05 error code, don’t worry! This is an issue you can usually fix yourself, and we’re here to help you through the process!

If you find out that you need any replacement parts for your air conditioner while you’re troubleshooting, you can enter your model number at AppliancePartsPros.com to order them. Most orders arrive in just two business days, and we have thousands of free guides to show you how to install your new parts.

Important: The troubleshooting information provided in this article may not apply to your specific appliance model. While we strive to offer helpful advice for DIY appliance repairs, variations in models and configurations can lead to differences in troubleshooting steps, error codes and part replacements. For the most accurate guidance, we strongly recommend consulting the technical sheet for your specific appliance model.

Safety precautions

When working on any appliance, remember to keep safety first. Here are some tips to keep in mind:

• Always power off and unplug your appliance or switch off the circuit breaker before you attempt any maintenance or replacement work. This keeps you safe by eliminating any risk of electric shock.
• If the appliance has recently been used, give it plenty of time to cool down before working on it.
• Take your time while working to prevent accidents and personal injuries. Rushing is the enemy of precision.
• Work in a well-lit area so you can see and access appliance parts.
• Keep your workspace free of clutter and other obstacles. Keep children and pets away from the work area.
• Never work on internal parts with wet hands. Make sure the work area is completely dry.
• Check the user manual to see if there are specific installation or safety instructions related to your appliance or replacement part.
• Be gentle when handling or removing parts. Excessive force might damage the appliance or cause personal injury.
• Wear insulated work gloves to protect your hands from sharp metal parts and debris.
• When working with wires, avoid touching any exposed wires or terminals. If you need to touch a wire, use a non-conductive tool or wear insulating gloves to prevent electrical shock.
• Always take photos or make a note of wiring terminals or other connections before disconnecting them to make reassembly easier.
• Don’t test live voltage with a multimeter if you’re unfamiliar with how to prevent short-circuiting.
• Consider wearing safety glasses and/or a dust mask when working with chemicals, dust or a large amount of debris to prevent irritation or injury.

Read more: How to troubleshoot & fix common window air conditioner problems  

How to troubleshoot the 05 error code

Follow these steps to find out what’s causing the 05 fault code on your LG multi-split air conditioner and how you can fix it yourself.

LIVE VOLTAGE WARNING: For this test, the appliance needs to be plugged in and powered on. Please be very careful to protect yourself from electric shock, which has the potential to cause serious injuries. Don’t ever test live voltage if you’re uncomfortable using a multimeter.

1. Turn on the power to the entire HVAC system.
2. Start the indoor unit in cooling mode and set the temperature to 65°F.
3. Set a multimeter to DC Voltage mode.
4. Within 3 minutes of turning the indoor cooling on, use the meter probes to test the voltage between terminals 2 and 3 on the outdoor unit to check the communication signal.
5. Check the meter. You should see fluctuating DC voltage between 0-65V. This is the serial communication signal between the indoor and outdoor units.
6. Use the meter probes to measure the DC voltage across the wiring terminals 2 and 3 at the indoor unit. The voltage reading on the meter should be identical to what you observed at the outdoor unit terminals.

If voltage isn’t present at the outdoor unit terminals, disconnect the inter-unit wiring, then use the meter probes to test the voltage on the wiring terminals again. If there’s still no voltage, then the outdoor power control board is likely faulty and needs to be replaced.

If voltage is present at the outdoor unit but not at the indoor unit, then the wiring between the units is the problem and needs to be replaced.

Read more: How does a MRCOOL mini split AC work?  

More information

Thank you for reading! We hope this guide helped you get your LG multi-split air conditioner working again.

If you have any other appliance repair needs or projects, don’t hesitate to explore our other troubleshooting guides and videos.

If you need replacement parts or some extra help with ordering them, grab your model number and head over to AppliancePartsPros.com, where you can chat with a pro, read our DIY blog and more.

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