[mycbarnes]

Without a schematic drawing and this being against common sense I'll ask the group first. My 120v air compressor will only run if the generator is running. With shore power connected and L1 and L2 power showing voltage on the panel this makes no sense. Shore power and no generator the compressor won't turn on. Know the demand is there, the air system would be below cut in pressure for sure by a bunch. The AC bus I wouldn't think would parse out the 120v generator power exclusive to the generator and or the auto ac power transfer switching for the bus do anything but all or none generator or shore power. Maybe a relay somewhere to switch compressor from gen bus to shore bus  but I don't see a reason why.
Terry