Every RV 1800 RPM Onan i have looked at had dual windings
But they were parallel connected inside the generator connections
For 120v
You will most likely need access to stator winding outputs
Break the parallel connections rewire in series for 230v
And possibly have to rebalance the circuit breaker circuits
The voltage regulator is set up for 120v and only senses one of the two output windings, to control the feild voltage on the rotor
Once you set the Onan for 230v output, then that is what you will have going to the breaker box, no way to get 120v only , except by using only one leg of the output for the house
So it will now be a stick house normal 230v input to breaker box
