A lot more info is really needed. How long does your coach sit between uses. Yes, You said the house batteries are plugged in all the time, that's good but that won't charge your chassis battery. There is also a parasitic drain on your chassis battery. A knife switch is a perfect answer, but will not tell you why it is draining. so back to the question, how long does it sit between uses. And yes, your dash radio is hooked up to your house batteries.
__________________
|