I need help to determine if the alternator is not working or if the regulator is the problem. I had a voltmeter connected at the battery while running, and it would vary from only reading the the battery voltage to intermittently reading 13.5 to 15-16 VDC. Is there a place to measure the input to the regulator? I do have a VOM to measure ac or dc. I see where the regulator is on the side of the starter, but I do not know where the alternator is located. The engine is a B&S Vanguard 18HP, model 356777, type 0113E1. The tractor is a Regent 18HP Hydro model 1694656. Any help would be greatly appreciated. For the time being I charge the battery before needing to use it. The battery drops to about 11.5 VDC after cutting (about 1.5 hours use). Thank you.