So your factory 35 Amp Mitsubishi Alternator sucks and can barely keep up with your headlights, heater and windshield wipers running at the same time? The Internal Voltage Regulator crapped out and now the truck isn't charging? You could buy a replacement alternator, exactly like your old one, but why?
Enter the Nippondenso Alternator, found on Dodge Caravans with the V6 engine and Dodge Trucks (1988 - 2001) with the 3.9, 318 and 360 TBI engines, Magnum V6 (3.9L) or Magnum V8 (5.2L / 5.9L). The lowest output Nippondenso puts out a whopping 90 Amps, many are 120 Amps, some are even higher (approaching 200 amps in some rare cases). The best part, all of them are the same external size and almost identical in size to the Mitsubishi Alternator found on D50 Trucks.
So, how do you go about fitting one of these monsters to a D50?
Step 1 : Find a Nippondenso Alternator (Find a Used One or Buy a New One)
Step 2 : Buy a Chrysler External Voltage Regulator and Pigtail (any chrysler product 1971-1987) For simplicity and guaranteed results on getting the right stuff, buy one for a 1973 Plymouth Duster. This regulator and pigtail are always in stock at every parts store. You'll have about $20 invested in the Regulator and Pigtail.
Step 3 : Swap the Pulley from your Mitsubishi Alternator to the Nippondenso Alternator (because most Nippondenso Alternators have a Serpentine Pulley, some Early 88-91 models have Dual V-Belt Pulleys though)
Step 4 : Loosen your Upper Alternator Bracket/Adjuster Bracket and rotate it up a little bit (about a 1/4" or so). The Nippondenso alternator upper mount ear is slightly taller than the mitsubishi alternator.
Step 5 : Wire up the Regulator Pigtail, connect the wiring to the alternator and add the Ground Strap from the Alternator to the Battery. The entire regulator harness only requires you to connect to 1 Wire from your original D50 Alternator Plug. The Blue Wire connects to the Blue Wire on the Regulator Pigtail (see attached photos).
Step 6 : Mount the Voltage Regulator. The best place is the Passenger Side Inner Fenderwell, about 6" in front of the firewall. There are already bolt holes (threaded) in the fender well in this location. It puts the regulator close to the alternator wiring, as well as the main wiring harness, should you choose an alternate Ign+ Feed
Step 7 : Reinstall your Belt.
It doesn't matter which of the 2 small field posts on the alternator you connect the Green and Blue Wires to, the circuit works exactly the same on either posts, but you must have the green on one post and the blue on the other. The Blue wire is the Ign + (on both the D50 and on older Chryslers) which supplies a field to the alternator and + to the regulator, the Green is a pulsed output from the regulator.
Congratulations, you now have a monster alternator that bolts in place of the factory alternator, is readily available at any parts store or junkyard. You also now have an easily serviceable/replaceable and readily available external voltage regulator that can be swapped in under 2 minutes.
The Initial Installation takes about 25 minutes on average, requires no permanent modifications to the truck, and makes it easy to service the charging system with readily available parts.