Is your house battery is good condition and properly connected ? Some convertors put out rough DC power and use the house battery to "clean it up" so it is suitable to power your 12V stuff. You may be able to download a manual for your convertor
here; or try using dogpile search engine.
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2000 Winnebago Ultimate Freedom USQ40JD
, ISC 8.3 Cummins 350, Spartan MM Chassis. USA IN 1SG 11B5MX,Infantry retired;GS Life member,FMCA
" My fellow Americans, ask not what your country can do for you, ask what you can do for your country. John F. Kennedy