This url will take you to a page for your unit, there is a download section where manuals are, in the operator manual section 4 page 21 there appears to only be an AC breaker. This manual does not have a wiring diagram unfortunately. I did find another manual with a wiring diagram, it showed 12 volts going directly to control board, I'll find it again and post link however while it's for a 3.6 not exactly the same model.
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwi4x9r9oKT6AhVIhIkEHY01CR8QFnoECBAQAQ&url=https%3A%2F%2Fwww.coloradostandby.com%2Fcummins-onan-3-6-ky-fa-26120-rv-or-commercial-generator-set-rv-qg-3600-lp&usg=AOvVaw2EMtr_TesUTaxXFTnvSi-u