Hi,

Anyone who can figure this out deserves a medal.

I have a basic chinese 9000 system (Mayoki). This is a no frills unit as I will describe. The fault is that the unit reaches 28 (on it's own display board) and cuts out, then back in at 30 irrespective of what the temp is set to. (The room temp IS genuinely 28)

Mechanically everything fully operational, gas charge, outdoor fan running full speed, good temperature at the air off vent and equipment begins to cool the room quickly when running.

First thoughts - temperature sensor faulty. Changed them (pipe and air sensors share a common plug on the PCB). No difference. OK so I think it could be the PCB itself not interpreting the information from the sensors correctly, or even self inducing the timer... So changed the PCB from an identical known good machine - no difference. For good measure I changed the display/receiver board too although I couldn't justify to myself why.

Went back to the job and studied the pattern. The outdoor unit is merely a slave. No electronics, no sensors, just typical 5 wire connection Live comp, live fan, live Rev valve, neutral & earth. It just does what the indoor PCB tells it to do, and is doing that job just fine. Indoor unit has a single main PCB to which is connected the evap fan, transformer, mains, flap motor, etc, etc. When the unit cuts out (early) the relay is heard to drop out, and power to the outdoor is terminated. So something is causing the relay on the PCB to drop out too early. If there was a fault on the indoor fan, this model would show a fault code and shut down, so apart from the previously mentioned sensors what else could cause the compressor relay to operate before it reaches the set temp?

Remote control works fine, all instructions are accepted by the unit, all figures match between remote and display... I am baffled

One last thing, Thinking that the pipe sensor might be picking up some liquid slug or similar, I have moved it from the pipe socket to just hanging in the cool air passage, no difference.

Any ideas please guys.

Trevor