Installing one wire alternator

One wire alternators ( one and only one connection to alternator other than case ground) have been around since the 70s and have been on millions of cars. They emerged when it became practical to miniaturize electronics enough to put the regulator inside the alternator. Custom car builders love them since wiring is very simple.

To me, there is only one downside to one wire alternators that are used on cars that are not driven everyday. Since the alternator has only one wire that is connected directly the battery, it can’t be “turned off“. This means that it is pulling a small amount of current all the time, about 75 micro amps (less than about a tenth of a milliamp) on GM alternators that I am familiar with. This will drain the battery in about a month or so, based on data I observed with a boat I had with one. If you don’t drive the car regularly, you need to unhook the battery or use a battery tender.