The OLD Onans(70's thru mid 80's) did not have a electric starter motor. The had a LARGE Armature that had BOTH DC brushes(slip rings) and AC brushes(slip rings). When you applied 12 volt power to the Onan, the DC brushes turned the Stator/Rotor(Armature assbly) to turn the Genset to starting speed. Then the AC brushes supplied the excitement for the AC output. Now, This OP's genset does NOT have a battery charger circuit IF he has the standard 12 volt starter motor. It DOES have the AC brushes and slip rings. IF the Genset sees NO 120 output power(Usually defective voltage regulator) the genset will NOT stay running when the Switch is let go. Also if the Oil pressure sensing system is defective. Doug
