mini split AOU18RLX problem

[Godeath]

Hello,I have some problem with a Fujistu mini split outdoor unit.After a electrical failure,the indoor unit gave me the code of "no communication".So I replaced the active filter module and the main pcb.The code disapear and I thinked "another sastisfied customer".4 hours after the custumer call back the a/c is not working anymore.When I arrived the compressor stop without any reason.No error code on the indoor or on the outdoor unit!.The pressions are just fine.The compressor is not stopping on the overload.Sometime the compressor stop at the same time of the fan condensor,sometime the fan run about 30 secondes alone.Everytime,before he stop,the compressor make some noise like he force and then stop.

Any suggestion or solution will be appreciate!
Thank

[bigor_2]

If you hear a sound similar to a sound working step motor then compressor possibly is defective. The compressor is mechanically blocked. Try to connect an equivalent of the compressor from lamps.

[Godeath]

hello bigor_2!If the compressor is blocked,the amps will rise up?As I remember,the amps seem to fall before the compressor stop.But I will check this again to be sure what I am saying.And if the compressor is deffectice,is it normal to have no error code?

[bigor_2]

My answer was based on phrase <So I replaced the active filter module and the main pcb>.
Active filter module it is component fujitsu inverter system. However marks RLX mean that system on R22, non inverter, heat pump. It's so?

[Godeath]

I am pretty sure that the outdoor unit is aou18rlx inverter.The refrigerant use is the 410A.Write:aou18rlx service manual on google and you will find this unit specification.

Maybe the active filter module is faulty again.Because I changed this one first and the error code do not disapear.Then I changed the main pcb and the code was gone.
So,I don't know if it's plausible,maybe the defective pcb damaged the new active filter module.

[bigor_2]

New active filter module and main PCB (IGBT module) no have heat-removing paste. The problem can be in it.

[Godeath]

It's interresting.The old active filter module had no paste on it but the pcb had some kind of white liquid more clear than a paste.I don t know if it act like a heat remover.

[Godeath]

The thermal paste doesn t chage anything.The unit still running 1/2 hour then stop.No error code,no clue of what is going on.

[nike123]

Try with 3 lamps of 500-700W (220V) connected in star instead of compressor. If lamps goes off after 1/2 hour you have faulty some PCB.

[Godeath]

Ok.Will try this tomorow.So the new pcb can be deffective.Thank.

[Koopy]

if the pcb defective?

y does it keep failing. solve that issue before walking away i suggest

[Mr.Ductless]

Call Fujitsu technical support, there are ways to ohm out the active filter modual and the IPM section of the maincontroller board. You can actually see if you have a defective board and determine which board it is. Typically both the ACTPM and the Main controller have to be replaced at the same time after a power faliure. Heat sink paste should be used on all components that make contact with the heat sink itself. If unit ran for couple hours after board replacement that is signature of board faliure due to overheating.

[Mr.Ductless]

The white paste is called heat sink grease, it improves heat transfer between the electronics and the aluminum heat sink to which they are screwed down. The fact the unit ran for 4 hours after board replacement is the giveaway that the boards overheated. Using this paste and screwing down all of these components firmly to the heat sink is absolutely critical when replacing boards. IPM, Bridger Rectifier, ACTPM are all components that need the paste. The ACTPM does not come with paste from factory but the manufacturer recommends applying it when replacing it in the field. Get new boards and use the paste, screw these components down and make sure not to trap any wires under them.