If your LG Multi V system is showing error 237, an indoor unit’s communications board has heard nothing from the outdoor unit for over three minutes.
What this means for your building
Multi V units exchange data continuously over an RS-485 communication connection. That link carries the instructions telling each indoor unit what to do and the status information coming back.
Error 237 is a timeout. The indoor communications PCB waited three minutes, received nothing, and the system flagged it.
The three-minute delay matters: it means this is not a momentary glitch. Brief interruptions do not raise this code. Something has genuinely interrupted communication for a sustained period.
As with most communication faults, the equipment is often perfectly healthy. What has failed is the connection between units.
How urgent is it?
Urgent, but not hazardous. No refrigerant is escaping and nothing is at safety risk. The affected zones have stopped and will not resume on their own.
The distinction worth drawing: a 237 that appeared once after a power event may have been transient. One that keeps returning is a connection getting progressively worse, and those do not stabilise.
What it typically costs
Low to medium, comfortably at the cheaper end.
The work is tracing an RS-485 connection through the building — checking terminations, verifying polarity, testing the cable. That is technician time rather than expensive parts.
Cost rises only where a communications PCB has been damaged, which typically follows a surge or a connection left arcing while the fault was repeatedly reset.
What causes it
- Damaged or disconnected communication cable — often from other trades working in ceilings
- Loose or corroded terminals at either end
- Reversed polarity on the RS-485 connection, particularly after work on the system
- Communications PCB fault at the indoor or outdoor unit
- An indoor unit that has lost power — it cannot communicate if it is off
- Electrical interference where communication cable runs alongside power or other building services
That third cause is worth flagging. RS-485 is polarity sensitive, and a connection reversed during a repair produces exactly this symptom while looking perfectly correct to the eye.
What happens if you leave it
Affected zones stay down, which in a commercial building means complaints the same day.
The longer risk is spread. Communication faults rarely stay confined to one unit. A terminal loose enough to drop the link tends to loosen further, and neighbouring units on the same run start dropping out too.
Repeatedly resetting also carries a hardware risk. A marginal connection left arcing for months is how an inexpensive cabling repair becomes a PCB replacement.
What we check
- Identify which indoor units are reporting the fault.
- Inspect terminations at the outdoor unit and affected indoor units for looseness and corrosion.
- Verify RS-485 polarity — reversed connections are a common and easily missed cause.
- Test the communication cable for continuity and damage across its run.
- Confirm power to every affected indoor unit.
- Check for interference sources where the cable runs alongside other services.
- Test the communications PCBs once wiring and power are confirmed sound.
What you can tell us before we arrive
- Which zones are affected? One unit or several tells us where on the run to start.
- Does it clear and return? That pattern suggests a marginal connection or interference.
- Has any work been done recently? Ceiling work, a fit-out, or service on the system.
- Was there a power event? Outages and surges are common triggers.
Related codes
- 05 / 53 — Indoor to outdoor communication. Related faults with a different diagnostic emphasis.
- 200 — Auto pipe detection failure. Communication problems can prevent detection completing.
- 242 — Network error. Central controller and remote controller communication.
Get the connection traced
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Related codes
CH05 and CH53 are communication failures between indoor and outdoor units. Shown as 05 and 53 on the outdoor display. The most common source of LG callbacks.
Error 200 is auto pipe detection failure. The system cannot work out which indoor unit is on which heat recovery port — and it recurs after any PCB replacement.
Error 242 is a network error at the central controller. Your building management interface has lost contact, even if the units still run.
Frequently asked questions
What does error code 237 mean on an LG Multi V system?
The indoor unit communications PCB has received no signal from the outdoor unit communications PCB for more than three minutes. It is a communication timeout, meaning the units have stopped exchanging data rather than any mechanical part failing.
What is RS-485 and why does it matter here?
RS-485 is the communication standard the system uses to carry data between units. Diagnosing a 237 involves checking that connection specifically — its wiring, terminations and polarity — rather than treating it as a general electrical fault. Polarity in particular is easy to get wrong and easy to miss.
Why does the code mention three minutes?
The system waits before declaring a fault, so brief interruptions do not trigger it. A 237 therefore means communication was absent for a sustained period rather than momentarily glitching, which points at a real connection or hardware problem.
What causes a 237 communication error?
Damaged or disconnected communication cable, loose or corroded terminals, reversed polarity on the RS-485 connection, a communications PCB fault, an indoor unit that has lost power, or electrical interference where the cable runs alongside other services. Reversed polarity after recent work is a common and easily missed cause.
How much does a 237 error cost to repair?
Usually toward the lower end for a VRF fault. Most cases resolve to cabling, terminations or polarity, which is diagnostic labour rather than expensive parts. Cost rises only where a communications PCB has been damaged and needs replacing.
Does 237 mean the same thing as CH05?
They are related but not identical. Both concern communication between indoor and outdoor units, but 237 refers specifically to the communications PCB receiving no signal across the RS-485 connection for a sustained period. The diagnostic emphasis differs. In practice both are traced along the same communication run.