Fujitsu ducted system intermittent cooling

[Magnum9]

I have a Fujitsu ART series ducted system (outdoor unit AOT54LJBYL) which is suffering from intermittent operation. If you select cooling it will cool for an hour or two (sometimes all day) then start blowing hot air. Sometimes simply stopping it and changing the mode on the indoor controller to auto will get it going again but just as often I need to turn off the main power to the unit to reset. There are no fault codes and no abnormal noises. When it is working it does not suffer any degraded performance.

Any ideas I could look at before calling a service guy?

[install monkey]

filters clean?

[Brian_UK]

What is the control set at?

[bigor_2]

Magnum9, easiest for you
1. check purity of indoor air filter as said install monkey
2. check purity of outdoor heat exchanger

*** 54LJBYL is regular visitor to RE

[Magnum9]

I have the control set to 24 degrees Celsius, indoor filter is clean and outdoor heat exchanger seems clean enough but maybe I could give it a blast with some water and see if it helps. The unit is almost 7 years old and I have not had it serviced in the last 4 years because I could not see the value in servicing something in which all the major parts are sealed.

[Magnum9]

Also should mention ambient outside temp was around 35 degrees Celsius.