I have a 5500w generac with less than 50hrs of run time.Unplugged the black cord comming from the power head unit and got a reading of 120v on one side 0 on the other.After an hour of running the 0 side produced 80v for less than 5min then went back to 0 and stayed at 0.I know its not the breakers because I am taking a reading before the breakers/outlets. I've read to check the brushes for being stuck.Any suggestions on what else to check would be appreciated.

Well I took the brushes out today to see if they were sticking but didn't really notice anything. Reinstalled them and did a volt test, all is good so one must have been stuck as I was getting only 110 of the 220v. I'm hoping thats all it was and not coincidence.