CS$121 Use in Geo Confusing By Rich Herrington In 1989 General Motors introduced a new line of vehicles called Geo. These vehicles were also sold by other manufacturers with a different model name. The Geo Spectrum was also known as the Isuzu I-Mark, the Geo Tracker was also known as the Suzuki Sidekick, the Geo Storm was also known as the Isuzu Impulse, and the Geo Prizm was also known as the Toyota Corolla. All of these vehicles were equipped with either Nippondenso, Delco-Remy, or Mitsubishi alternators as original equipment. The Geo Tracker and Suzuki Sidekick use a Mitsubishi alternator that uses the “L” and “IG” terminals to operate. The “L” terminal does not have any power output. The “L” terminal goes open to shut off the dash light. No other relays are powered by this circuit. See Figure IT. Figure II [| (oe The Geo Spectrum and Isuzu I-Mark both use a Nippondenso alternator that uses a regulator that only uses the “IG” and “L” terminals to operate. The “L” terminal puts power out to operate one or more relays. (See Figure II.) The 1989 to 1992 Geo Storm and the Isuzu Impulse use either the Nippondenso or the Delco-Remy alternator. The Nippondenso alternator uses a regulator that only uses the “IG” and “L” terminals. The “L” terminal puts power out to operate a number of relays. (See Figure II.) The Delco-Remy alternator uses a 411 series regulator that is plugged into a powered circuit built into a separate plug. This power circuit plug is attached to the outside of the alternator with two screws. This is the only way that this alternator can function correctly in this vehicle. You must use some form of power circuit to operate all the relays within this vehicle. (See Figure IV, p. 16.) In the 1993 and later models of these vehicles, Delco-Remy has replaced the power circuit plug with a pass through plug. They have also replaced the 411 series regulator with the 440 series. The power requirements on the later model vehicles have also been decreased. You cannot replace the early model version with the later model version. However, you can replace the later model version with the early model version. The 1989 to 1992 Geo Prizm and the Toyota Corolla also both use Nippondenso and Delco-Remy alterna- tors. The Nippondenso alternator uses a regulator that uses the “S,” “IG,” and “L” terminals. The “L” terminal only puts out a small amount of power to shut off the charge light. (See Figure III.) Figure III IG L The Delco-Remy alternator uses a 411 series regulator and a different power circuit plug mounted on the exterior of the alternator. This circuit did not have the same amount of power output as the one used in the Geo Storm (See Figure IV.) Figure IV In 1993 Delco-Remy replaced this with an alternator using the 440 series regulator along with a direct pass through plug. The 440 regulator differs from other Delco regulators. It is turned on through the “IG” connection instead of the “L” connection as in other Delco regulators. The Toyota Camry also uses both Nippondenso and Delco-Remy alterna- tors in some models. This vehicle uses a CS130 series alternator when equipped with the Delco-Remy alternator. The “L” terminal in this power circuit plug goes to an open condition to shut off the charge light in the vehicle. Again, all three terminals perform a function. The Nippondenso alternator used on this vehicle also uses the “S,” “IG,” and “L” terminals. Different companies have made adapter plugs to replace the power circuit plugs that were used on the Delco-Remy alternators. Some work in one application or the other and some will work in all. Make sure that you are using the correct replacement. Determining the difference between these regulators and regulator/plug combinations has also proven to be a problem. In this portion of our Tech Tip we will try to explain how to determine which regulator or regulator/plug com- bination you are working with. First, in all the Mitsubishi and Nippondenso applications you need to use a device that will allow you to test the regulator functions either on your regulator tester or on your alternator test bench. Using proper testing equipment will allow you to verify that the “C,” “S,” or “D” functions are correct for the vehicle that you are building the alternator for. In the CS121 and CS130 Delco versions the procedure becomes a little more complex. Again, you need to use a device that will allow you to test the regulator functions on your equipment. If you are working with an alternator that had the power circuit plug as original equipment, your alternator was equipped with a 411 regulator. You can- not replace this combination with the 440 regulator and a pass through plug. Again, the 411 regulator turns on through both the “IG” and “L” terminals while the 440 regulator only can be turned on through the “IG” terminal. To determine the difference between the “IG,” “L” power circuit plug and the “S,” “IG,” and “L” power circuit plug on original equipment is simp