Help is needed in finding the cause of my battery drain. I have a 33' Beaver patriot. Cat 330 diesal 2000. I purchased two new batteries 1000 cca. Have 14.2 v when running. Shutdown I go to 12.2 immediately. I took to mechanic what a nightmare, he had coach for almost 4 months and could not find what was causing drain. After 4 months all he did was install a disconnect switch. Coach already had a factory disconnect switch this is an additional. So when operating I have 14.2 V. Shutdown drops to 12.2 instantly. Now I have to use disconnect switches to isolate batteries otherwise batteries would drain below 12.2. Now I come back a week later check voltage. Chassis batteries 5 V. Of course disconnect switches are in off position. Turn on disconnect switches chassis batteries go to 12.2. Ok, run engine. Showing 14.2. Shutdown, voltage drops immediately to 12.2. What is causing this immediate drop in voltage? All it is going to take is for me to forget to shut off disconnect switches when I shut off engine and have dead chassis batteries when I go to start a couple days later. There isn't much running off chassis batteries there main purpose is starting. To have such a big drop in voltage immediately after shutting down has me at a loss?? Please provide any thoughts, recommendations.
2000 beaver patriot concord 33' cat diesel 330, toad honda crv