Have a Bolens G16XT with a Briggs Opposed twin. Model is 402-437 Type is 0131-01 My amp gauge does not register anything, + or - . Have not had any luck finding a wiring diagram for this engine/tractor set up. It has an external regulator on the top of the left head tin work. I am not sure which wire is the charging wire from the regulator and where it is to go on the rest of the electrical. Any Ideas?