Panasonic ac unit keeps coming up with a fault.... the error code is F90 air con is 5kw

This is telling you there is an error which you will have to find by putting the remote control into service mode. Hold the check button on the remote for about 5 seconds and the display will change to --. Then press the timer up or down buttons to scroll through the error codes. When the indoor unit beeps quickly for about 4 seconds, you have found your error code and can narrow down your search for the fault.

Carrier Split Air Conditioner Error Codes - AC Error Code

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Jan 25, 2015 - REMOTE CONTROLLER FOR AIR CONDITIONER (SPLIT TYPE). Carrier Split Air Conditioner Error Codes. 00-01-02-03. 11-12-04-05.

Air Conditioning Fault Codes

F90 = PFC control
Abnormality judgement: 4 times occurrence within 10 minutes
Location to verify: Voltage at PFC

F90 - various defects of the compressor windings, defect in the inverter board Panasonic

try resetting by turning power off and on

Should be current detect pcb faulty, or compressor drawing too much current.
I don't have your model a/c, but panasonic fault codes stay pretty much the same
Normally panasonics have this info on the inside of the access panel.
Plus fault codes from the indoor unit make it easier to look up.

if the compressor is running, check the amps and refrig pressures.

The F90 fault indicates that the maximum time allowed for oven door unlock was exceeded. The control attempted to unlock the door. The door lock motor or mechanism failed to unlock the door within the maximum amount of time it is allowed to be energized by the control board.

It is unlikely that you will be able to reset this fault code. You can try to completely disconnect electrical power and leave it off for 5 minutes. After reconnecting power, the fault code will probably reappear since the control will still detect that the oven door is locked. The only way to clear the fault code is to disassemble the range and repair or reset the oven door lock assembly. You will need a service technician to complete this repair.

Check that your water pump is working and not blocked up as the unit will keep swicthing off if it can not get rid of the water.