Air was not cooling but indoor fan was working. Checked outdoor unit, fan not working and hearing like a vibrating/humming sound.

14.2.2 To Make a Diagnosis1 Timer LED starts to blink and the unit automatically stops the operation.
2 Press the CHECK button on the remote control continuously for 5 seconds.
3 "- -" will be displayed on the remote control display.
Note: Display only for "- -" (No signal transmission, no receiving sound and no Power LED blinking)
4 Press the TIMER ? or ? button on the remote control. The code "H00" (no abnormality) will be displayed
and signal will be transmit to the main unit.
5 Each press of the button (? or ?) will increase error code
number and transmit error code signal to the main unit.
6 When the latest abnormality code on the main unit and
code transmitted from the remote control are matched,
Power LED will light up for 30 seconds and a "beep" sound
(continuously for 4 seconds) will be heard. If no codes are
matched, Power LED will light up for 0.5 seconds and no
sound will be heard.
7 The breakdown diagnosis mode will be canceled unless
pressing the CHECK button continuously for 5 seconds or
operating the unit for 30 seconds.
8 The LED will be off if the unit is turned off or the RESET
button on the main unit is pressed.
Diagnosis
display Abnormality / Protection control Abnormality
Judgement Emergency operation Primary location to verify H00 No abnormality detected - Normal operation H11 Indoor / Outdoor abnormal communica
tion > 1 min after starting
operation Indoor fan operation
only • Internal / external cable connections
• Indoor / Outdoor PCB H14 Indoor intake air temperature sensor
abnormality Continue for 5 sec. - • Intake air temperature sensor (detec
tive or disconnected) H15 Outdoor compressor temperature sensor
abnormality Continue for 5 sec. - • Compressor temperature sensor
(detective or disconnected) H16 Outdoor Current Transformer open cir
cuit - - • Outdoor PCB
• IPM (Power transistor) module H19 Indoor fan motor mechanism locked 7 times occurance
continuously - • Indoor PCB
• Fan motor H23 Indoor heat exchanger temperature sen
sor abnormality Continue for 5 sec. O
(Cooling only) • Heat exchanger temperature sensor
(detective or disconnected) H24 Indoor heat exchanger temperature sen
sor 2 abnormality Continue for 5 sec. - • Heat exchanger temperature sensor
(detective or disconnected) H27 Outdoor intake air temperature sensor
abnormality Continue for 5 sec. O • Outdoor temperature sensor (detec
tive or disconnected) H28 Outdoor heat exchanger temperature
sensor abnormality Continue for 5 sec. O • Outdoor heat exchanger temperature
sensor (detective or disconnected) H30 Outdoor discharge air temperature sen
sor abnormality Continue for 5 sec. - • Outdoor temperature sensor (detec
tive or disconnected) H33 Indoor / Outdoor wrong connection - - • Indoor / Outdoor supply voltage H38 Indoor / Outdoor mismatch (brand code) H50 Ventilation motor abnormality 7 times occurance
continuously - • Indoor PCB
• Ventilation motor H51 Nozzle lock abnormality 2 times occurance
continuously - • Nozzle H52 Limit switch abnormality - - • Indoor PCB H97 Outdoor fan motor mechanism locked 2 times occurance
within 30 minutes - • Indoor PCB
• Fan motor H98 Indoor high pressure protection - - • Air filter dirty
• Air circulation short circuit H99 Indoor heat exchanger anti-freezing pro
tection - - • Insufficient refrigerant
• Air filter dirty F11 Cooling / Heating cycle changeover
abnormality 4 times occurance
within 30 minutes - • 4-way valve
• V-coil F90 PFC control 4 times occurance
within 10 minutes - • Voltage at PFC F91 Refrigerantion cycle abnormality 2 times occurance
within 20 minutes - • No refrigerant
(3-way valve is closed) F93 Compressor rotation failure 4 times occurance
within 20 minutes - • Compressor F95 Cool high pressure protection 4 times occurance
within 20 minutes - • Outdoor refrigerant circuit F96 IPM (power transistor) overheating pro
tection 4 times occurance
within 30 minutes - • Excess refrigerant
• Improper heat radiation
• IPM (Power transistor) F97 Outdoor compressor overheating protec
tion 4 times occurance
within 10 minutes - • Insufficient refrigerant
• Compressor F98 Total running current protection 3 times occurance
within 20 minutes - • Excess refrigerant
• Improper heat radiation F99 Outdoor Direct Current (DC) peak detec
tion 7 times occurance
continuously - • Outdoor PCB
• IPM (Power transistor)
• Compressor

Note:
"O" - Frequency measured and fan speed fixed.
The memory data of error code is erased when the power supply is cut off, or press the Auto Switch until "beep" sound heard following by pressing the "CHECK" button at remote controller.
Although operation forced to stop when abnormality detected, emergency operation is possible for certain errors (refer to Error Codes Table) by using remote controller or Auto Switch at indoor unit. However, the remote controller signal receiving sound is changed from one "beep" to four "beep" sounds.

If the outdoor unit is running the indoor fan should definitely be running. Turn power off to indoor unit. Put red green and yellow wires together behind the tstat with a wire nut. That is power (red), indoor fan (green), and compressor (yellow.) Turn power back on. This is bypassing the tstat and you should have indoor fan and outside running as well. If yes the problem is in the tstat, if no indoor fan the problem is in the unit. Good Luck!! Let me know!!

If you need further help, reach me via phone at https://www.6ya.com/expert/thomas_092728000e6acb79

I assume you are referring to the indoor fan coming on. If the fan on the outdoor unit is coming on, and the compressor is not, you have a control problem with the outdoor unit, I recommend calling a service man. Make sure you have power to the outdoor unit. There should be a service disconnect on the outdoor unit, connect and disconnect the power, you should hear a hum when the power comes on, put your ear to the housing of the outdoor unit and you will hear the power come on when it is turned on. If no power, or hum, check your breakers in the house electrical panel, see if any are tripped. Next step call a service tech.

Good. When it calls for cooling the wire conncets to a contactor in the outdoor.
Unscres the center of contactor and then check the contactor by pressing thr' ur screw driver maually. Just only for 5 seconds.
If it works, the contactor coil is defective.replace contactor

Indoor or outside. Im pretty should the compressor has gone. If you turn it on does the indoor fan and outdoor fan work but not cooling . or does it not turn on at all.
have you checked your fuse box.

While running, feel the bigger pipe outside, under the black insulation. If it is cold to the touch and if condensation is building up on it, that is a good indicator that it is properly charged. If it is warm, and you can hear the compressor running (humming noise while outdoor fan is running), that is a good sign that the unit is undercharged. The only way the unit is under charged is there is a leak somewhere. Do not let anyone tell you that the refrigerant needs to be swapped, or has gone bad, or just needs to be "topped off". The system should be perfectly sealed, and without leaks. First, I would check to see if the outdoor unit is running with the indoor unit. Then I would check the big pipe to see if it is cold. Hope this helps.

This is called a heat pump where the Reversing valve switches the flow of freon in the opposite direction.If you have the stat set for cooling, you need to go out side to the condensing unit to see if it is on.If its not running, there is an elect. box mounted near unit. You could have a blown fuse.Change both and see if it comes on. Check the breaker also to see if it may have tripped.The indoor unit will run without the outdoor unit running. If it was running when you went out, the fan should be running. Listen closely where the copper lines enter to see if you can hear the compressor operating. You cant mistake the humming sound. If all is running, it could be a freon problem, or if the fan is on and the compressor is not, you could have a open Run cap?. It could be several things, but i would check the things I have noted and we can go from there. I hope this takes care of you're problem, and please feel free to let me know. I am hear to help you.
Good Luck,
Shastalaker7
PS There is a sequence of operation on all units, and to be a service Tech, you have to know this. Just remember, if the outdoor unit isn't running, then you will not have heat or cooling.

I have run into this with the LG brand systems. try shutting power off to the outdoor unit to reset all units. If problem persists, it could have to do with a charge level of refrigerant (freon) or possibly a failed control board.

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/cody_17f08cf8e340c06c

More then likely it's the transformer. It may be getting weak. I've seen them hum/vibrate almost new and last for years. It's more an annoyance than anything.

This can only be a gas problem.
the split units goes on on and off if a shortage of gas is involved, the chances that you would here it wont be that big for the fans would make too much noise.
get a repair man for a re gas and all is well.

Good luck.

Wouter.