GM Upgrade to a CS Alternator

Why go through the trouble? Well, the GM SI alternators are easier to get and have higher outputs.SI is short for Systems Integrated which means the regulator is inside the alternator case. The CS alternators are even better!

The GM 10SI Alternator

All 10SI have three terminals (including those with a 1 wire regulator).

Typical SI Sources

If the one wire alternator is for cleaning out wires, you only need to retain the BAT wire. The 1 and 2 terminal wires can be eliminated. Don't be surprised to find that the Field wire only goes a short way into the harness and spliced into the BAT wire. The 1 wire regulator comes with a dust plug for the 1 and 2 terminals.

AC Delco wiring package 1870921 (for those 6 to 12 volt conversions) for wiring up a 10SI. This contains the terminal connector AND an extra resistance wire pigtail to connect to the ignition system (don't use a ballast resistor if you use a resistance wire). Also available is an ammeter package (1965400). Another piece (pn #8077 and 8078) is available from AC Delco for upgrading to a CS style from an SI. These SI-to-CS adapter plugs have a Molex connector to fit the existing wiring harness SI style connector, and the Delco Weather Pack connector to fit the CS-130 and CS-144. The AC Delco #8077 is used if you have a lamp on the dash and the #8078 has a load resistor for use with no lamp.

Alternate part numbers for the dash light version pigtails are Haywire P/N 2110 / Painless Wiring P/N 30707. General Motors P/N12102921 / Pico P/N 5331 are for no dash light installs.

Pulleys can be interchanged between the old externally regulated and the 10SI/12SI/CS-130, and even with the old externally regulated FORD alternators.

Always use a voltage gauge to monitor your charging system.
Don't expect your alternator to do anything for you at idle speeds. Alternator output increases with rpm, even a 100 amp unit won't put out much more than a 63 amp unit at 1000rpm.

The CS130 / CS144 Alternators

In 1986 GM introduced the completely new, 105-amp, CS130 Delcotron alternator (CS130 = Charging System with 130 mm diameter stator) because the SI series alternators could not keep up with the increased electrical demand and because overdrive transmissions were lowering engine and alternator rpms. The CS130 weighs less, is smaller in diameter but uses the same 6.6" mounting-hole, center-to-center distance, uses less internal parts, has a better voltage regulator system, has increased durability and is less noisy (audibly and electrically) than the SI alternator it replaced.

There is also a 120-amp, CS144 version if you need more output because you're running large amounts of electrical equipment in your vehicle such as high-powered stereos.

Typical CS Sources

The 105 amp version size is close to typical SI alternator. So you can use the original brackets. Typical SI alternator is only 63 amps and at higher RPM's than what the CS's need. In other words, at idle, the CS is putting out, where as the SI is just spinning.

The 105 amp CS130 alternator can be found on late-80's GM truck or full size car with mounting ears that are 180-deg apart. Most will come with a serpentine belt pulley so you will have to change over your pulley if you are still using a V-belt.

The flange for the tensioning bolt and the alternator bracket are tapped for metric bolts so you will need to get 8 x 1.25mm bolts. The alternator bracket may need to be modified and you will probably need a couple of washers to take up the space between the alternator bracket and the new alternator.

Most of the connectors for the CS alternators are four wire but will only use two of them and the wiring is the same as the SI.

CS series wiring pin-out:

CS Install Note: The switched 'light' (terminal 1 on SI or 'L' on CS), must have 12V switched power with between 35 and 350 ohm resistance *** If below 35 ohm, the CS units will not work! *** That resistance is normally the bulb! If you try to be "custom" and use a LED, there isn't the correct resistance and the alternator will not work correctly! You can't just by-pass the light! You may need to add a resistor to this lead. Some documentation suggests that a switched power source can be connected to the 'F' terminal instead, where there is supposed to be an internal resistor.