Stuart,
Yes, it's an external system. I bought a new 3-wire, 80 amp alternator from Summit several months ago. I installed it along with a new regulator and discovered just last night in pouring rain that my truck is running on battery power only-as the lights got dimmer and dimmer. Just as I pulled into my driveway, the engine quit due to no juice. After I charged the battery it runs again and all lights work. I checked the alternator and it's putting out 12+V depending on rpm so I think it's the regulator that went out.
Terry
