Alternator swaps and general charging system performance

Part 1- GM

 

This article is an attempt to sort out some of the confusion arising when swapping engines and powertrains into older cars, while at the sane time maintaining or improving electrical system performance, which is often lacking in performance vehicles and hot rods.

I would also like to make one point about modern automotive electrical systems that seems to be misunderstood by some.   Prevailing thought seems to place the battery at the center of the automotive electrical system.  In the days of the DC generator, this was partially true, but in modern vehicles, with electric power demands ten-fold or higher than the typical 1950s vehicle, this is not true.  The alternator supplies all the power for operating the powertrain and accessories, while the battery is present primarily for cranking the engine and providing auxiliary power for accessories until the engine is running.  The alternator is the heart of the modern electrical system, and proper application, installation, and connection is crucial in a modern powertrain, where it is required to provide clean, well-regulated power. The battery still plays an important role as a filter for the alternator and providing surge to large transient demands for current from devices such as winches, hydraulic pumps, and ridiculously large stereo amplifiers.  With this in mind, let’s discuss some of the common alternators you are likely to encounter on a GM engine swap:

 

 

Delco CS-130 Alternator and variants

 

The Delco CS-130 alternator was used from the mid eighties through the mid nineties in many GM vehicles, especially light trucks.  It is an improvement over the venerable 10SI alternator used throughout the seventies and eighties, being more compact, with better cooling (albeit still with an external fan), ball bearings both ends, and smaller diameter slip rings for longer brush life (lower surface speed).  It is typically rated at 105A, which is probably as much as can be supported by the small case and cooling system.  Another notable improvement is the regulator, which employs a MOSFET field driver, and has the capability for remote sensing, frequency output, failure light, and remote turn on.

Those features are available on a 4-position weather-pack receptacle (see upper photo):

 

 

As you may have noticed, there are two variations in the pinout, the first being the standard GM implementation, and the second being the “1 wire” regulator version marked by many speed shops and online.  I strongly recommend that you do not use the one wire variants, for the following reasons:

1.     Without remote sense, voltage regulation is poor, and because of the voltage drop from the alternator to the battery, the charge time is significantly increased

2.     Without remote turn on, there is a small parasitic load on the battery, which will deplete the battery if the vehicle is not driven regularly

3.     Many PCMs use the “S” terminal as a frequency input which is proportional to engine RPM, this can be used as a secondary tachometer signal, or to detect belt slippage.

4.     Many of the “one wire” regulators have an excessively high voltage setpoint (typically 14.7V), which can damage the battery, especially in hot climates, and can also damage entertainment systems, etc.

5.     If you want the idiot light to work, you are out of luck.

 

Having addressed the downside of a one wire installation, let’s review what is needed to do it correctly:

1.     Obtain the correct pigtail, or better yet the plug and pins, so you don’t need to splice wires.

2.     Connect the “S” (sense) wire battery positive (or as close to the battery as you can)

3.     Connect “I” or “IGN” to ignition (key switch)

4.     Connect “L” to one side of the ALT lamp, the other side of the lamp goes to IGN., alternatively, a 470 ohm, 1W resistor can be used in place of the lamp if you don’t have or desire the lamp.

5.     The “STA” (stator) terminal may be called for by the PCM/ECU, usually only in an OEM installation, or, in the case of a GEN3/4 swap, if the PCM is configured to take it.

 

 

Delco (Delphi)AD-230, AD-244 Alternator and

Bosch DR-44/244 (4 wire connector)

2 wire variants

         

 

The 230/244 series of alternators used in GM vehicles beginning in the mid- nineties, are, in my opinion, one of the best light vehicle alternators ever.  They routinely last 200K+ miles with no maintenance, and even then, brushes (and bearings while you’re at it) are usually all it takes to freshen them.  This alternator, with its internal cooling fans, has extremely effective cooling, coupled with less noise.

The 230 series is approximately 105A, the 44/244 series are 130-180A, depending upon model and year. 

The earlier units with a four-pin connector are to be preferred, as they are more flexible, and because of their remote sensing feature, better for vehicles with high electrical demand.

The Connector is labeled P-L-F-S

P is the stator (tachometer) output

L is lamp, or excitation wire

F is the field duty cycle signal output

S is sense, for remote sensing

The P connection may be called for in an OEM application and can be used as a tachometer with some aftermarket tachometers and electronic dashes (not likely to be needed).

The L connection will excite (turn on) the alternator, either through a lamp (NOT an LED), or through a 470-ohm, 1 watt resistor to IGN voltage.

The F connection may be called for by a GM PCM, but likely is not needed.

The S connection is the remote voltage sensing connection, to be connected as close to the positive battery post as possible, for best charging and system regulation.

 

There are also Bosch version of these alternators, known as the DR44 and DR44G

The AD 230 is a smaller variant, typically used in smaller trucks and vehicles with less electrical demand (approximately 105A)

There are, after 2003 two pin connector versions of both the 230 and 244 series that use a PWM input to control the alternator output from the PCM.  These should not be used unless you have a PCM that is programmed to drive them, as the adapter to make them work costs as much as an alternator.  (it shouldn’t, but it does!).

 

 

Old Reliable- the 10SI

(and children)

 

The GM 10SI alternator is probably the most produced alternator on the planet.  Introduced in 1970 and debuting on the Corvette, it didn’t look much different from the 10DN it replaced, except for the fact that the regulator was missing from the firewall.  It had a nifty little module that did all the work without relays buzzing and falling out of adjustment.  Not only that, but if it broke, it was easy to fix, with just a few small hand tools.  Very elegant for the time.  And it’s still being built, all over the world, and it is still readily available, and inexpensive.

The original version was rated at a paltry 37A, but over the course of years, it would go to 55, 67, 73, and finally 78A.  Limited primarily by cooling ability.  There are many variations of the 10SI, most involve different case clocking, stator wire size, and voltage setpoint for the regulator.  (The standard GM regulator works well in most climates and has an internal thermistor that will reduce the voltage slightly in hot conditions and raise it in cold.  This tends to keep the battery at an optimal charge condition.  There are extreme cold and extreme heat regulators available from distributors).

A slightly revised model, the 12SI, introduced in 1979 with a much better cooling fan and open case construction, would push the design to 105A.

There was also a large case 27SI, used in large cars (Cadillac, Olds).

This is probably the most common alternator for hot rodders, as it is easy to mount, and is capable of sufficient output for most non-fuel injected applications.

The 10SI is often sold as a “1 wire”, my advice is still- don’t do it. Unless you have a carbureted, simple street rod or race car with very undemanding electrical loads, the electrical performance with a properly excited, and load sensing alternator is much better with respect to battery life and system voltage regulation.

The two connections in addition to the output post are for the alternator lamp and the remote sense.  Connecting the sense lead as close to the battery terminal as possible will ensure more rapid charging and better system regulation.  The lamp/excitation connection can be used with an existing alternator lamp, or can be connected through a 470-ohm, 1 watt resistor to ignition.  Personally, I like having the “idiot” lamp, as it informs you immediately of a charging system failure.

The remote sense goes to the battery, the lamp wire goes to the lamp, which then goes to ignition power.  If you want to skip the lamp, connect a 470-ohm 1 watt resistor in place of the lamp.  If you add a lamp, be sure it is a tungsten filament lamp, and not an LED assembly.  LED assemblies will not typically pass enough current to excite the alternator.

 

Notes

 

This document is not intended to be an all-encompassing manual on GM alternators, it is intended instead to inform hobbyists as to what they can do to get the most satisfactory operation of their automotive electrical system.  I did not cover the original 10DN and 20DN GM externally regulated alternators, as they are becoming difficult to source, and their performance and reliability is inferior.

If you are a purist and insist on using these alternators in your restoration, that is great!  They can perform adequately, especially in a stock application with minimal electrical demands and non-voltage critical loads.

Also, there are and will be newer and systems that are beyond the scope of this document.

Later, I will provide some information on Ford, Chrysler, and third-party suppliers such as Motorola, Leece-Neville and Prestolite. Also, I hope to include foreign manufacturers such as Bosch, Lucas, and Nippon Denso (ND).

 

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