OK, guess I am confused a little but am wondering if you may have a converter issue instead of a inverter issue. Most lights in a camper are 12 volts, same as in your car or truck except for lights in a slide out which may be 110 volts or should be. An inverter turns 12 volts to 110 which would run your microwave if wired in that way into the fuse box. A converter changes 110 to 12 volts and runs most lights, power side of refrigerator while on propane and lights the furnace and water heater (which you state is bypassed) and charges the in house camper battery. The reason you may be hearing the converter kicking in could be the converter is damaged or the battery itself is low on water or going bad. Just thoughts. Most factory converters are not known for being very sturdy or big enough to run the power needed. Sorry this may not be the answer you are looking for.