Alternator Improver
Scott Moody - smoody@redstone.army.mil
Introduction
Here is a low-cost way to increase the output of your GN's alternator. You can set the output voltage to whatever you desire within reason and have it operate via a switch. It requires some parts that are available at Radio Shack or other electronics parts outlets. The basic operating principle is that this scheme utilizes the "sense" terminal of the alternator's regulator. The function of this "sense" is to do just that; to sense actual battery voltage and adjust alternator output accordingly. In stock configuration it is connected internally and regulates the voltage at the alternator output. What we want to do is to ratio the sensed voltage to some lower number, in effect "fooling" the regulator to perceive a decrease in voltage. The corrective action taken will then be to increase output voltage. This may or may not increase your performance.
Circuit Diagram
Circuit Diagram
Circuit Operation
The circuit operation is pretty simple following the potentiometer rule. Vbat is the open-circuit (no-load) voltage, the actual system voltage will be lower. The design equation:

Vbat = Vs x (R1 + R2)/R2

Vs is the alternator regulated voltage, i.e. the voltage at the stock alternator bat terminal, usually around 13.6 volts. For the 0.25 watt resistors R1 and R2, keep the sum of R1 + R2 to 2500 or greater.

Example, Vs = 13.6, R1 = 430, and R2 = 2200 gives 16.25 volts at the alternator output (bat. terminal).

Increase R1 to increase Vbat, decrease R1 to decrease Vbat.
Connect one end of R1 to the Bat terminal, the other end to common ("c") on the switch. Connect one end of R2 to switch common, the other end to ground. Connect switch normally open ("n.o.") to the "s " terminal of the alternator connector. You will need a terminal to fit the connector; try GM (#12015858), Packard Elect., junkyards, or auto electric rebuilders.
The switch controlling circuit operation can be a microswitch mounted under the TPS or a pressure activated switch (at say 10 psi boost pressure like the GN digital dash pressure switch from GM). Optionally you could replace the two resistors with an adjustable potentiometer (2.5 k ohm, .25 watt) which would allow you to vary the voltage as you like. Be sure to check operation with a good digital voltmeter. If there are any questions, call me at (205) 876-3628.


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