Rex:
On my Contessa, 330 hp Cat, the ECU draws a continuous ~2 amps, thus depleting the chassis batteries unless there is a functional charging system in place. In 98, the system came with an echo charger, but of course, by 2011, when I got the coach, that was well past its sell-by date and was non functional. I put in a "BIRD", a Blue-Seas brand relay that combines the house and chassis batteries for charging, but keeps their loads isolated from one another. No subsequent problems. The BIRD was easily found at an RV supply store in Indio, so you should have no trouble finding one. As the brand name implies, Marine stores will also supply that item.