My generator was running great until I suspect a little extra load tripped the breaker on the unit. I pushed it in, felt a click, assumed that was the problem. However when started there was no power in the house. When I checked the generator outlets the 110 volt worked, nothing on the 220 volt. I tested voltage and found 120 volts from ground terminal to each leg. From neutral to one leg 120, neutral to other leg nothing. While testing with volt-ohm meter, voltage came back, no idea why. 4 wire plug looks perfect, no signs of burning. I don't feel I can depend on the unit now, anyone have any ideas?