Daikin mini split heat issue

[Ntdk1212]

Looking for some advice/answers. I have a 36k outdoor unit with I believe 4 ports but currently only using 2. I have a ceiling mounted cassette that’s 15k and a wall mounted unit that is 9k. And have the heat pump option. 

My issue is with the big cassette. It doesn’t have automatic on or off, so the fan is always blowing when on A/C. When on heat the the fan is not always on and only turns on with the heat sporadically. I’ve seen it turn on anywhere from 1 min to 45 mins and anywhere in between. I could turn it all the way up to 90f and it doesn’t turn it on any more. Any ideas? Thanks.