As far as alternators go, General Motors has used only a few basic designs as the standard alternator in their cars & light trucks since the alternator was first introduced in the 60's. The first alternator offered by GM was the externally regulated 10-DN. This alternator was very dependable. The 10-DN was followed by the  SI series with internal voltage regulator. The early lower amperage SI series alternators were quite dependable. Toward the end of this alternator's cycle, the amperage demands were increasing and reliability decreased. The SI series alternator was followed by the CS-130.  This alternator was a complete design departure from the earlier SI series. The CS-130 alternator at 11 lbs. and up to 105 amps pushed new ideas at reducing the size and weight, yet upping the amperage output requirements over eariler models. This CS-130 has been plagued with many problems. Problem areas include rear bearing size, rectifier design, air flow, heat dissipation and overall cooling. One of the biggest problem areas with this alternator has been with the rectifier shown in figure 1 & 2. The rectifier is used to convert AC current produced by the alternator into DC current for use by the vehicle. The rectifier is made of two halves, the negative bridge and the positive bridge, each bridge consists of three diodes. During the power conversion process, these rectifiers produce heat. If heat builds up in the rectifier, it will fail. To rid the rectifiers of excess heat, they used the heat sink transfer process of bolting the rectifier to a flat surface in the alternator with heat transfer compound between the rectifier and the housing. The first problem with this situation was the lack of adequate surface area to sufficiently dissipate the amounts of heat being generated. The other profound failure in reducing the overall size of the alternator was the decision to "stack" the rectifier's negative and positive bridges as shown in figure 2. Delco-Remy engineers were required to reduce the overall size of the alternator. They placed the positive half of the rectifier directly on top of the negative rectifier. This made for heat dissipation problems and frequent failures. In the mid 90's, Delco-Remy redesigned the CS-130 alternator and produced the CS-130D Version. They took great strides in upgrading the alternator to deal with the misgivings of the earlier CS version. They increased the thermal mass, installed larger bearings, incorporated dual internal fans, went to a more open design for improved air flow and moved the voltage regulator and rectifier from the inside to the outside rear of the alternator for better cooling. All of the modifications helped the reliability of this alternator greatly. The only problem with the CS-130D alternator is the fact that they kept  the same "stacked" style rectifier that they had all kinds of problems with in the earlier CS-130 alternator. Finally, in 1999 GM first introduced the new AD-230 alternator. For 2002 it is the most commonly used standard alternator on GM vehicles. The AD-230 alternator is very similar to the CS-130D, fact is many parts are interchangeable. The improvement in the new AD series alternator that I get most excited about is transmogrification of the inferior "stacked" rectifier to a superior "logical" design. On the AD-230, the rectifiers are kept separate, a negative side and positive side as shown in figure 3. In my opinion this new design has the chance of increasing this alternator's reliability and life expectancy to that of the early SI series alternators.  figure 4&5 show how much larger the heat dissipating surface area for rectifier cooling on the new AD-230 alternator is. The mating surface for the rectifier  goes almost all the way around the rear circumference of the alternator as shown in figure 4. For comparison figure 5 shows the older "stacked" rectifier of the CS-130/CS-130D alternators sitting on the new AD-230 rear housing. As you can see, the heat dissipating contact surface area of the AD series is almost double that of the CS alternator. Plus, in the "Stacked" rectifier design of the CS-130D you have the heat of the positive bridge adding to the heat of the negative bridge and vice versa.

BETTER LOW RPM CHARGING:
The CS/AD Millennium alternator also incorporates the improved stator rotor combination offered by the AD series. This improved design produces a better magnetic field between the stator and rotor causing the alternator to start charging at lower engine RPM's. If you've ever experienced voltage drop or lights dimming at idle this new combination can help.

EASIER REPAIR: Quick Start has made repair of the new AD Millennium Series Alternator, the easiest fix since GM first introduced alternators in 1964. On OEM AD series alternators, the stator leads are welded to the rectifier. To change the regulator/rectifier assembly you will need to cut these welded connections, then extend the stator leads and solder them to install the new rectifier/regulator assembly. NOT  WITH QUICK STARTS new AD/CS Millennium alternator.  All new AD/CS Millennium manufactured by Quick Start have ring terminals on the rectifier and stator lead connections.  With the removal of just a few screws the complete rectifier and regulator assembly (Figure 6) can be changed on this new alternator, greatly simplifying the repair process. The repair is so simple that if you have enough room behind AD/CS Millennium Alternator,  you can change a defective rectifier/regulator assembly with the alternator still mounted on the engine.