I don't believe there is a port for adding refrigerant. With mine: 2x year I remove roof cover and hose out the bugs, dust, debris from the works. I then remove inside cover, and vacuum out all build up on the coils and plenum. I wash the filter as needed. Another thing I check frequently is the foil tape in all ceiling vents to make sure that no cooled air is leaking into the attic space. This seems to keep mine running good.
2013 Keystone Sydney 340FBH 5'er
2012 Silverado 3500HD, SRW,LTZ,4x4, Z71, Crew, 6.0 Gasser, 4:10 Gears, Standard bed
"These days, I have problems in areas that I used to not have areas", so life is good.
Clean it and check for air / water leaks. These are not serviceable I've been told bye 3 techs and several other campers .. Unless its electronics the "freon" can't be serviced it leaks it's junk. I just replaced mine last year.
Ditto all prior poster does.
My post's are my opinion The advice, comments etc are free and worth what you paid
Clean the coils 'regularly, and in extreme humidity and heat keep the fan on low instead of high.
And do NOT let anyone tell you you can add freon. My first RV the service guy said it needed freon and I let him do it. Fast forward a couple of years and I needed repair service to look at 'just the fan' and he opened the lid, slammed it closed and said he couldn't work on it because someone had tapped the line to add freon and that prevents him by law to work on the unit.
With all the regulations in place regarding freon if he even just replaced the fan he would loose his license.
"We must be willing to get rid of the life we've planned,
so as to have the life that is waiting for us".