This is my first post. My name is Kyle. I have a Coaire natural gas tank-less water heater that is suppose to still be under warranty. Unfortunately the company shut down and parts are no longer available. The issue i'm having is no hot water or heat. Well, I have hot water SOMETIMES. If I pressure up the system It will hold pressure while the hot water is running. I can have a shower, run laundry or the dishwasher, and I have plenty of hot water. Once I shut off the taps, the system slowly loses pressure and drops to zero and throws an error code. This system has a built in expansion vessel that doesn't seem to be building pressure. Maybe a few PSI after the system has been running. What should the internal expansion tank be running at/holding at PSI wise? Everything ignites fine, the pumps seem to be running fine and I cant find any leaks. I have told I need a brand new heater by some "unreliable" sources. Looking for some good advice. Thanks so much guys.