Advice with Daikin RZQ125B8W1B problems

[ijf65]

Hi Guys
I am not that familiar with daikin ACUs and have the following situation.
there is 2 identical ducted Super inverter units (RZQ125B8W1B outdoor units with FBQ125B8V3B indoor units) First one shows fault H4 ( Low pressure fault ) however pressure is OK and low pressure switch also seem to work ok. I have assumed that problem is coming from PCB so i have taken the PCB from the other one and swapped it but the fault is still there. I don't know what could be the problem . Any suggestions?????. The second one was working initially but it was low on gas so i have vaqued it out and recharged it with R410A. Now it shows fault L5 which is compressor winding down to earth.so i have swapped inverter PCB from the other one but fault is still there. It could be compressor fault for real but it was working OK and i wonder was it this regasing the problem. and maybe i did not do something right. I need to get at least one of them working and any help would be greatly appreciated. If not i will have to buy new one but in that case there is another problem as indoor units are buried over the ceiling and cannot be removed. Is it possible to use the same indoor units but with different outdoor units as RZQ125B8W1B is too old and is difficult to find.
Is there also way to switch off error message from remote and force unit working.
Thanks in advance for any repply

[r.bartlett]

Are you F-Gas registered?

[ijf65]

Yes I am F-Gas Registered. I am in the trade for about 10 years and i have some experience.

[r.bartlett]

H4 is low pressure switch faulty. I would have changed that first.

Take the LP off the L5 unit and see if you can get the first one running...

check the wiring etc...

not being there we don't know what you did or how well you did it.. either way it don't look good for the customer...

[leegally1983]

Have you flooded the compressor on commissioning?? i.e. where and how did you charge it?
Have you checked the windings on the compressor?

The other unit sounds like a faulty LP switch try swopping one or linking it out

[Brian_UK]

The daikin fault finding flow chart will give you guidelines to establish the fault.