LG code Mode conflict

LG multi-split: one outdoor unit cannot heat and cool at once

On an LG multi-split, every indoor unit has to run in a compatible mode. Learn why one room set to cooling stops another from heating.

Source verifiedBy HVAC Bench Editorial DeskLast reviewed
Direct answer

What this means

LG states that on a multi-product system every indoor unit connected to one outdoor unit has to run in cooling only or in heating only. Cooling and dehumidification cannot run at the same time as heating, while air purification and fan modes are unrestricted, so one room set the wrong way stops another from getting what it asked for.

Equipment and model context

LG multi-split systems where several indoor units share a single outdoor unit, as described in LG help-library guidance

  • LG multi-split outdoor units
  • LG multi-split wall indoor units
  • LG multi-split ducted indoor units

This applies to LG multi-split arrangements where several indoor units share one outdoor unit. Heat recovery systems, which are a different architecture, can serve simultaneous heating and cooling, and single-split installations have no conflict to resolve. Confirm how many indoor units your outdoor unit serves.

What you may notice

  • One room refuses to heat while another is cooling, or the reverse, with both units apparently working.
  • Whichever indoor unit lost the argument is the one showing a code, while the unit that won carries on without comment.
  • Changing the mode on an unrelated room makes the affected one start working.

Likely causes

  • A single outdoor unit produces either heating or cooling at any moment and cannot do both for different rooms.
  • An indoor unit left in cooling or dehumidification in an unoccupied room still participates in the decision.
  • Automatic mode on one unit can select an operation that conflicts with what another room has requested.

Diagnostic paths

A room nobody uses is set to cooling

A spare bedroom, office, or unused space has an indoor unit left switched on in cooling or dehumidification while occupied rooms are asking for heat.

Switch the unused unit off entirely rather than changing its set point. An indoor unit that is off does not participate; one that is on in a conflicting mode does.

Someone is using automatic mode

Somewhere in the house an indoor unit has been left in an automatic mode, choosing heating or cooling for itself rather than following an explicit instruction.

Set every indoor unit explicitly to the same mode during a season. Automatic selection on a shared outdoor unit produces conflicts nobody chose.

It resolves when another room is changed

Adjusting a unit in a different room makes the affected one begin working, which appears unrelated until the architecture is understood.

Treat that as confirmation rather than coincidence. A fault that moves when a different room is changed is describing shared capacity, not a component.

One compressor, one direction at a time

A multi-split runs a single refrigerant circuit with one reversing arrangement. Whichever way it is set, every indoor unit on that circuit is downstream of the same decision, so the modes have to agree.

  1. Outdoor unitOne compressor and one circuit
  2. ReversingSets heating or cooling for everything
  3. Indoor unitsAll served by that single decision
  4. ConflictArises when requests disagree
Which modes can coexist on one LG outdoor unit
ModeCompatible with heatingCompatible with cooling
HeatingYesNo
CoolingNoYes
DehumidificationNoYes
Fan and air purificationYesYes

Why the room that fails is not the room at fault

The confusing part of a mode conflict is that the complaint arrives from the wrong place. A bedroom will not heat, so the bedroom unit gets investigated, and there is nothing wrong with it. The setting causing the problem sits in a different room, sometimes one nobody has entered for weeks.

That makes this one of the few faults where the useful action is to walk the house rather than to examine the equipment. Every indoor unit on the system, including ones that are switched on and forgotten, is part of the decision.

The seasonal changeover that catches people out

Conflicts cluster around the changes of season, when a cool morning follows a warm afternoon and different rooms want different things on the same day. A household that ran cooling all summer and now wants heating in one room discovers the rule at exactly the point it is most annoying.

The habit that avoids it is simple: at the turn of a season, walk the house and set every indoor unit to the same mode, switching off the ones nobody needs. LG's own guidance says the conflict clears once every unit is set compatibly. It is also worth explaining to everyone in the house, because the person who leaves a spare room in cooling is rarely the person who finds the bedroom cold that evening. The single against multi-zone comparison covers why this architecture gets chosen in the first place, and the LG mode conflict code page covers the specific code some systems display when the requests disagree.

Service handoff

What to give the technician

Tell the technician how many indoor units share the outdoor unit, what mode each was set to, whether switching the others off resolved it, and whether the affected room works when it is the only one running.

Homeowner safe

Safe homeowner checks

  1. Walk through every room with an indoor unit and note which mode each one is set to, including any that are switched on but unused.
  2. Switch off indoor units in rooms nobody is using rather than leaving them running in a conflicting mode.
  3. Set every remaining unit explicitly to the same mode rather than relying on automatic selection.

Is a reset appropriate?

Nothing needs resetting for a mode conflict, because nothing has faulted. Operation resumes as soon as the requests agree, which is why setting every unit to one mode is the test as well as the fix.

Stop point

When to call a technician

  • A conflict that persists after every indoor unit is set to the same mode is no longer a mode conflict and needs the system examined.
  • Changing how a multi-split is configured, including adding or reassigning indoor units, is installer work rather than a settings change.

Questions people ask about this

Why will one LG room not heat while another cools?

A single outdoor unit produces heating or cooling at any moment and cannot do both. LG states that every indoor unit on one outdoor unit must run in cooling only or heating only for this reason.

Does dehumidification count as cooling?

LG groups it with cooling for this purpose, so a room running dehumidification conflicts with a room asking for heat. Fan and air purification modes are unrestricted and coexist with either.

Can any multi-zone system do both at once?

Heat recovery systems are built to serve simultaneous heating and cooling, and they use a different architecture with additional components. A standard multi-split does not have that capability.

Evidence record

How this page was checked

official manufacturer support article · checked 2026-09-15

Every technical claim above was written from primary documentation held in the HVAC Bench evidence record: LG Electronics technical literature. Where a source limits a definition to certain models, test conditions, or product classes, that limit is repeated here rather than generalised.

Documentation class
official manufacturer support article
Scope of the definition
LG multi-split systems where several indoor units share a single outdoor unit, as described in LG help-library guidance
Last checked
2026-09-15