All, I posted this at DIYMA, and didn't get too may helpful responses, so figured I'd ask the Hive Mind. Back in the '90s, I used to set amp gains by turning the level pot all the way up and then ...

I'm having problem with a starter motor on a riding mower, and need to check if the motor is getting juice and not working or if something else isn't working and no juice is getting to the starter.