On the covered LG air conditioner, CH 90, CH 91, F4 means a fault raised during the test run phase to prevent damage to the appliance — LG's own wording. LG notes some models display this as F4. First, note whether the error followed installation or relocation.
Differential
Likely causes of “LG air conditioner code CH 90, CH 91, F4”, and how to tell them apart
- 1
Wrong wiring or a pipe connection at install
What separates it The code shows during the first test run of a new unit
How to confirm LG lists incorrect wiring, an unfinished test run or restricted refrigerant flow; the installer checks the pipe connections
- 2
A one-time electrical glitch in normal use
What separates it The code appears in a unit that has worked for months
How to confirm Switch off the circuit breaker for about 5 minutes, then restore it
Try in this order
0 of 6 completedWhat to do first
ReversibleNote whether the error followed installation or relocation.
Correct only the documented fault domain
ReversibleLG directs that the piping connections be checked by the installation technician.
Reset the power
ReversibleUnplug the unit or trip its breaker, wait about 5 minutes, then restore power and start it.
Call the installer if new
ReversibleOn a unit installed in the last days, go back to the installer; LG says to have the pipe connections checked.
Understand that it is a test, not a failure
ReversibleLG's error-code guide says CH90 and CH91 (shown as F4 on some models) appear during the test run that follows installation, to protect the unit. The air conditioner is not broken.
Let the test finish or cancel it
ReversibleWait for the test run to complete, or cancel it with the remote or controller buttons the unit's installation manual names. The manual for your model says which button stops the test.
Evidence ledger
Sources behind this answer
Exact questions
Common questions
What does CH 90, CH 91, F4 mean on a LG air conditioner?+
a fault raised during the test run phase to prevent damage to the appliance — LG's own wording. LG notes some models display this as F4.
Why does F4 show instead of CH90?+
On some models the same test-run fault is displayed as F4.
Why does my new LG air conditioner show CH90 or CH91?+
Those codes show while the unit is in its installation test run. Finish or cancel the test run to return to normal operation.
Is F4 the same as CH90 on an LG air conditioner?+
On some models the test-run message appears as F4 instead of CH90 or CH91.
Should I call a technician for CH90?+
Only if the code stays after the test run ends. The installer who commissioned the unit can confirm whether it is still in test mode.