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LG Air Conditioner CH04 Error Code

Drain problem or water tank full. Here is what it means and how to clear it, easiest fix first.

CH04
Moderate DIY

The unit has detected that condensate water is not draining as it should. On ceiling-mounted units, LG points to a drain pump that has stopped working, a drain hose that is clogged or runs uphill, or a filter clogged with dust. On window and portable units, water has simply built up inside faster than the unit can get rid of it, which is common on humid or rainy days.

Some window and portable models show FL instead of CH04. On these units cooling can still work normally while the code is shown. On ceiling cassette and ducted units the code relates to the built-in drain pump and drain path. Check your owner's manual for your model.

Safety first: unplug the air conditioner (or switch off its breaker) before touching filters, hoses or panels. If you smell burning or gas, or see water near the outlet, stop and call a professional.

How to fix LG CH04

  1. Clean the filter

    Switch off the unit at the breaker (or unplug a window or portable unit) and slide out the air filter. Rinse it in lukewarm water, let it dry fully and refit it. LG suggests cleaning the filter about every two weeks.

  2. Drain a window or portable unit

    Unplug the unit first; if water has reached the cord or outlet, switch off the breaker instead of touching the plug. Set a shallow pan that holds at least 1.6 qt (1.5 L) under the drain port at the lower back (some models have two ports), remove the drain cap, let the water run out, then screw the cap back on firmly.

  3. Fit a drain hose if it keeps happening

    On window and portable models, you can attach a drain hose of the size LG specifies, about 0.7 in (18 mm), so water runs away continuously. On an exterior wall, route it so it doesn't drip on anyone below.

  4. Check where the drain line comes out

    On ceiling-mounted units, look at the drain line where it leaves the house or empties into a drain and clear away any dirt or debris you can reach from outside. Then reset the power at the breaker.

When to call a technician

If a window or portable unit shows the code often even in dry weather, or a ceiling unit's code returns after a reset, have the drain pump, float switch or internal drain line inspected.

Parts that commonly cause CH04

Order parts by your exact model number so they fit.

Other LG air conditioner codes

Frequently asked questions

What does CH04 mean on a LG air conditioner?

The unit has detected that condensate water is not draining as it should. On ceiling-mounted units, LG points to a drain pump that has stopped working, a drain hose that is clogged or runs uphill, or a filter clogged with dust. On window and portable units, water has simply built up inside faster than the unit can get rid of it, which is common on humid or rainy days.

Can I fix LG CH04 myself?

Often. The first steps above are safe checks a homeowner can do. If they don't clear CH04, the cause is likely a worn part that needs replacing.

What if CH04 keeps coming back?

A code that returns after a reset and the checks above usually means a part is wearing out. Note when CH04 appears (which cycle, how often) and have your model number ready; it helps a technician bring the right part on the first visit.

Last reviewed 2026-10-19. Codes and steps can vary by model; check your owner's manual.

References