LG LSZ182M-4 wiring diagrams, serv manual?

Hi all, long time lurker, infrequent poster.

I have a large client who has one of these units in their house and seems to be getting the runaround from people who haven't got a clue. So they have asked me to have a look.

The job is certainly a "do the important client a favour" as it is 4 hours travel. So I am trying to get as much info as I can before going. One thing that seems odd is that they say it is powered from an internal plug, but I haven't ever seen a 410A inverter from anyone doing this. Many fixed speeds systems yes, inverter no.

They are being told that the entire unit needs replacing and a needed component of this is going to involve a few $K to run another single cable to the condensing unit which is on the roof of their building. I can't understand this at all, given that it should be easy enough to use the theoretical reduced number of existing lines and commonality b/n lines at the head with a bit of clever thinking to get correct isolation techniques at the condensing unit. That is....if it actually needs an extra line at all....and is it actually needing replacement at all blah blah...hence the need for a wiring diagram etc.

To me it simply sounds like incompetence at basic troubleshooting (which seems to be a disappearing art these days....more trial and error "haven't really got a clue" type fixing), hence me going to have a look. Thus any prior knowledge would be a great help. I've only put in a few LGs many years ago.

Any help or links greatly appreciated. Goggling brings up very little of what I want, but it appears that parts are still readily available. It could also be that I only have a pic from them of the head label, and this ID might not actually be the correct complete model reference. edit: So it might be possible that the unit isn't actually an inverter (although the references I have found say it is), just LG using common heads b/n model types.

cheers, and thanks for any help

Aussie