repair guy found that it had a pressure sender that screwed into the low side line. I think he put a "T" on that and was able to top it off from there. It might be worth the cost of a service visit. It could be just a pressure adjustment. Another time my system started to give me trouble and the fellow told me the pressures were all wrong and did some adjustment. It worked fine when he walked away but started doing the same thing a couple of weeks later. He came back and changed some kind of valve and it worked fine. That's been two years ago. I've had units that have lasted 15 years and were still going strong when I sold the boat. I have two systems aboard now. One for the freezer and one for the refrigerator and they were installed in 2003. One is the one above with the pressure issue and the other has never missed a beat. Find a good guy and have him take a look. Based on what he says, make your decision.