B&S 17HP OHV INTEK charging circuit

Greetings!  I've got an old Ariens EZR-1742 with a B&S 17 HP OHV INTEK engine that won't charge the battery.  It's model 311777-0154-E1.  While troubleshooting, I discovered that one of the wires from the voltage regulator/rectifier was broken off and despite hours of disassembly and searching, I can't find a place to reconnect so I can continue troubleshooting.  The voltage regulator is type 491546 and only has two wires - one red and one yellow, both going to pin connectors.  The red one connects to a purple wire (assuming that is my DC charging circuit - positive) but the yellow one is connected to a black wire that was somehow sheared off.  I can't find any wiring diagram consistency that tells me where it should be connected - some say it's a "magneto kill switch" (but no indication where to tie it in) and another says it is AC power source (my mower has no lights or AC power use).  I can't troubleshoot sufficient to determine what parts I need until I get past this issue.  Any ideas?  Many thanks!