Supermarket Case question

[70runner]

First off, I will explain my situaiton. i am a Grocery store owner. I know some of the basics of the commercial refrigeration just through experience dealing with this stuff. We are 100 miles from the nearest guy who has a lot of experience with commercial equipment. So, I started useing a younger Tech that is closer.

My problem is this, I have a Dairy case, open front 13feet long 7 feet high 5 shelves counting the bottom. MP39. Low side pressure is 15, high side is 160. Coil temp is 26 degrees, the case temp won't get below 46 degrees. The tech is a heck of a nice guy but he isn't figureing it out. I don't want to call someone else just yet. So I thought I would ask here what else could be the problem and maybe bring that up with the tech. He admits he is inexperienced in commerciel refrigeration but I really don't know if he can call someone or not to get advice.

One more thing to know, is the inside temp in the store is 80 degrees, New air conditioner in a couple of weeks should help that, but I don't know if that really affects the dairy case as much as it seems because produce case isn't having any issues and another identical case for cheese etc, isn't perfect but a lot better than the dairy case.

Any advice I can pass on is apprecieated.
Thanks