Well, you could put an ammeter in series with the positive cables for the house battery and see how many amps (or probably more like micro amps) are being drawn. Once you know that, you’ll know how hard you need to look for what is using power (assuming any automatic loads are turned off as well i.e. water pump, clocks, refrigerator if LP/electric adsorption type, etc..).
For the chassis battery - todays radios consume power all the time, even when turned off (keeps the clock synched). It’s enough to run a battery down in a few weeks.
But again, put an ammeter in series with the positive cable and see how much current is being drawn.
Are you certain to turn the antenna boost switch off? Mine will burn the chassis battery down in about 4 days if I forget to turn off.
Parasitic loads (micro current loads that are near impossible to find) are not uncommon in MoHo’s and rv’s - so much so that battery disconnect switches are easily found at CW, WalMart, and maybe even BassPro/Cabella’s.
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