Figuring it out without manuals
So, I'm troubleshooting my Hehr Powerline alternator running a Powerline 3 terminal isolator that the 3rd terminal is not charging house batteries but goes to a coil. I'm also determining why there's an adjustable negative rectifier wired to the batteries.
The rig is a Roadmaster chassis, '92 Monaco with 8.3 Cummins with MD3060.
Had dead batteries, replaced them, ran an alternator load test through my external battery charger and an alternator fault showed. Luckily I'm at home and it's safely parked outside.