Unfortunately you do not give me enough information for me to even guess what is causing the problem. But there are a couple of things that you can do prior to taking your RV in and having a Certified RV Technician take a look at your Air Conditioner.
The first thing to do is check the filter that is on your Air Conditioner. It is located under vent cover on the AC unit inside your RV. Most RV Air filters can be cleaned by rinsing them off with some water and mild dish soap. Make sure that you thoroughly rinse the filter off with water after using the soap and put the filter back in place when it is dry. A dirty filter will cause inefficient cooling.
When you remove the filter you will also be able to see the evaporator coils, if they appear dirty you should clean them off as well.
After you have done your cleaning chores, you should test the Air Conditioner unit again and see if that has solved the problem. If not then you will have to take it in and have it checked out. There are several other things that could be causing your problems from a bad compressor, bad relay board, etc. and most of these items are not serviceable by a do it yourselfer RVer.
I am not familiar enough with your area to make any recommendations on where you should get the job done. Your best bet is to contact a local RV Dealer and see where they recommend you take your RV for service.
Sorry that I could not be of more help.
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