ONAN discontinued using low oil level switch on the KY gen before yous was made. Bad idea to run less oil....keep it at full mark...only holds 1.5 qt, no oil filter or oil pump, so does not have low oil pressure switch either...so change it often...oil way cheaper than parts and labor bills. No high temp safety switch on these...make sure you run with service door installed, or it will overheat. Your spec is also just before Onan started putting diagnostics into control board, so no help there, either. I would check fuel delivery..OP stated fuel pump may be getting hot and quits pumping....happens a lot on these units.
Also voltage reg. may be heating up and failing. Also verify thaty 12+ battery voltage is being supplied while running. These sets do not have integral batt. charger...so depend on RV charger converter to keep bat volts up. If voltage drops too low, control board and fuel pump quit working...and shut down!! 1250 hrs not too long for brushes...but have
seen them worn out with much less hours. I think if brushes were problem, would not run even for short period of time
