Hi all

I have the machine mentioned in title. Was installed second hand and couple of issues getting going - a U4 error and another which i forget but i think was pcb related. Then it started working and was cooling ok.

The system is 12.5Kw but we have about 8 indoor units amounting to 17.5Kw. We didnt have them all on at the same time. Pipework is spread accross 6 floors. It worked ok for about a week but then last week with the hot weather it was failing. I would turn off outdoor unit, leave for a while and then hold reset and power cycle. That fixed it a few times but then it died and we were left with L9 code and the fans and compressor arent coming on (lights are on though).

As far as i can determine, this means we have either a faulty inverter pcb or refrigerant loss or maybe dead compressor. The refrigerant was just checked so that should be ok. It appears that the PCB is a common problem so i wonder how you check that other than just replace it (if you can find one).

What advice does anyone have for troubleshooting without spending lots of money?

Many thanks
Ash