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   Powermaster supplies Marken Performance with alternators and starters for everyday use or racing.  Powermaster's 12si family of alternators is not only a great high output replacement for early GM 10dn and 10si alternators, but they work remarkably well in the generator to alternator conversions.  The one-wire alternator, identified by the single post in the rear of the unit, is the easiest to install and wire into an existing charging system.   A generator creates energy by rotating a conductor inside a stationary magnetic field. Alternators create their movable energy more efficiently by rotating a magnetic field inside conductors. 

   3-wire alternators begin working when the ignition switch is turned on whereas 1 wire alternators work as soon as the sensing circuit built in the internal voltage regulator senses rotation of the alternator’s rotor.  

   A 1-wire alternator has a turn on point (sometimes called “cut in”, which is typically 1200 engine RPM’s).  This is the speed where the internal sense circuitry connects the battery to the voltage regulator, thereby turning the alternator on. Once the voltage regulator turns on, the alternator will remain on and charging until the engine comes to a complete stop.  Many of the Powermaster one-wire alternators can be used with the OE style plug if the removable cap is removed from the OE hook up slot.  The one-wire charging wire is connected in the single pole sticking out of the back of the alternator.  To ensure a proper ground it is recommended that you use a ground strap/wire and use the "optional" grounding strap threaded receptacle in the alternator’s rear case. 

   For the rest of this article a 1960 Chevrolet C20 Apache Fleetside pickup is used to convert the electrical charging system from the stock generator to a modern 1 wire 100 amp PowerMaster 12si Alternator (part # 7294). Part # 47293 is 150 amps. 
   The generator that you will be removing is much longer than the alternator you will be installing.  You will need a generator to alternator conversion mounting bracket. We used the Alan Grove Components alternator mounting bracket (part #224L) designed specifically for the 6-cylinder 235/261 Chevy engines from 1955 through 1962.
   Because the new 1 wire alternator has an internal regulator, there is no need to keep the external regulator and wiring going to the regulator. Sometimes builders leave the voltage regulator in place with the wires unhooked and taped off with electrical tape in case they want revert back to a generator charging system in the future. Keeping in mind that our objective is to make our project truck a dependable daily driver, there was no chance that we were going to be needing the stock voltage regulator again. We gave it the old “heave ho” and taped up the wires.  Installation is simply installing the new mount, installing the alternator, attaching a charging wire to the battery or starter/starter solenoid, from the alternator, and adding a secondary ground wire from the alternator to the block.  The Powermaster alternator bolted into place, leaving a lot more room than the original generator took up. The drive belt was checked to ensure the pulleys were in alignment and the belt was tightened “alternator tight.”  if the belt is too tight, it can transfer that pressure to the bearings which will wick away the grease and lead to bearing failure. So, tight enough to prevent slippage but not overly tight.  Now the 1960 Chevrolet C20 Apache Fleetside pickup has no more dim lights at night slowing down for a stop sign. This is a necessary safety upgrade for vintage cars and trucks that are intended to be daily drivers. 


   Suggested charging wire size (4-7 feet max):

     30-70 amps = 8 gauge
     70-100 amps = 6 gauge
   100-150 amps = 4 gauge
   150-200 amps = 2 gauge

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