My air conditioning daikin models nr is.(FTY50gaval)work 30 minutes and than stop it self for 30 minutes.

What is wrong with that? Does it get too warm when it's cycling?
There might be a min-max setting, or an energy saver setting, that you can change.

It could be just cycling, but if the outside coils are dirty it could be cutting on and off on the high-temp overload in the compressor. Check the outside coils and see if they are dirty, if so, clean them by turning off unit and spraying on a foaming coil cleaner available at an air conditioning parts store. DrTom4444