Why Convert to A One Wire Alternator

The one wire alternator has been around for several decades. Originally designed by GM for use in industrial and farm equipment, a clever hot rodder grabbed one and installed it on their ride and a simple and easy to use alternator upgrade was born. These original alternators were often a 10si Delco model (you can use our GM alternator guide to learn more) but today you can find direct fit one wire alternator conversion alternators for just about any engine or accessory drive system.

The benefit of a one wire alternator conversion is the simplicity of its wiring needs. Unlike stock alternators that require additional wiring for the external or internal voltage regulator, the one-wire alternator variant simply needs a single wire from the alternator’s charging stud directly to the battery’s positive terminal, or a positive terminal junction connection, such as a starter solenoid on the fender or directly on the starter itself.

When we asked Tuff Stuff’s Mike Stasko about charge wire sizing this is what he had to say: “If you are going to add or use one of our higher amp alternators you have to use a larger diameter charge wire.” As such, the single charge wire that the typical one wire alternator conversion requires must be properly sized for the alternator’s maximum output capability. The larger the amp load the larger the wire diameter (smaller gauge size number) you must use. An 8 gauge wire will suffice for a standard 55-65 amp output, while 65-100 amp output should use a larger (numerically smaller) 6 gauge wire. Anything over 100 amps a 4 gauge wire must be used to provide enough support for the amperage output from the alternator.

The 1-wire alternator uses an internal voltage regulator that self-regulates the alternator’s output. There is no need for the traditional external voltage regulator found on many earlier generator and alternator charging systems found in early hot rods and cars up through the early 1970s. The self-sensing voltage regulator used in single wire alternators does not need a switched 12-volt exciter circuit wired to it like a 3- or 4-wire alternator with external regulator. This self-exciting voltage regulator only needs to see a certain engine rpm to connect the battery to the regulator and begin charging. This is often in the 1,200 rpm range.

Having too low of an alternator output for the application will mean that your charging system will often use your battery’s reserve capacity to keep up with electrical demands. You should have enough charging system capacity that your battery is essentially used for starting the vehicle and for short term key-on engine-off electrical demands. We asked Tuff Stuff’s Mike Stasko to elaborate further: “You need to add up all the amperage and whatever that total is, typically you want 20 to 25 percent more amperage than what your total usage is.”

While the GM term gets added on to the description a lot, there are 1-wire alternators for many non-GM applications as well. Some are based off the GM 10SI alternator case, while others use a Ford or Mopar alternator case for easy mounting in factory brackets and for those where a factory-style alternator is desired from a visual standpoint. The following links are sorted by application to help you find the best one wire alternator conversion for your build.