It all STARTS with knowledge of how things work!
REMOTE VOLTAGE-SENSING IS THE KEY TO GOOD ELECTRICAL SYSTEM PERFORMANCE... It lets the voltage regulator make adjustments where proper voltage level will do the most good.
Remote Voltage Sensing is not a new idea; in fact many factory original systems have been using it for years (even with external voltage regulators back in the 1960's).
All voltage regulators take an electrical system reading, and constantly monitor the voltage level of the system. For most temperatures and conditions, the textbook battery voltage level when topping off a fully charged battery is about 14.2volts (with a 12 volt system). The voltage regulator will adjust alternator output in effort to maintain that 14.2 volt level, under normal operating conditions. Therefore, most electrical system parts (lights, ignition, and accessories) are designed for best performance when operating at about 14volts. Electrical system performance drops off abruptly when voltage delivery to the parts is only slightly low-and so we really like to see those parts operating at 14volts!
With involved wire harness construction used to deliver power to various parts of the electrical system, some of the wires will be long in length. Most often, the dash area with switches and fuse box is far from the alternator. And under the hood, the battery may be at the opposite side from alternator mounting, which will also require a long wire. The long length of wires will result with "voltage drop."
Considering the spread-out location of electrical system parts on the car, often the most efficient and practical layout is to route alternator power output to a centrally located "junction." And then from the junction, power will be distributed to various parts of the electrical system. Also the electrical current used to charge the battery will be routed from the central main junction to the battery. The diagram above shows such a system; and it is a system that was successfully used with many factory-built wire harness layouts.
The key to good performance with the layout described above is to let the voltage regulator make adjustments to voltage level at the junction. (And then the voltage at the battery and other parts of the system will follow the voltage level maintained at the junction.) The voltage regulator can maintain 14.2 volts at the junction, even though the junction may be many feet of wire from the alternator. But REMOTE VOLTAGE-SENSING must be enabled to make it all happen. The diagram above shows this basic layout; and it was successfully used with many cars during the Muscle Car period. Certainly the Chevy design layout was this type during the Muscle Car period. (Although the particulars and location of components did get moved around during that period of years.) When using this factory wire harness layout, and up-grading to modern and more powerful alternators; it is of critical importance to let the voltage regulator read and adjust voltage at the junction. And we call this function "REMOTE VOLTAGE-SENSING." ("REMOTE" because the voltage regulator takes care of voltage level at a place away from the voltage regulator, alternator, and battery.)
The photo above shows an actual "main junction," which we removed from a Chevy factory original wire harness. Note that the splice used for the factory "junction" was crimped and soldered; these factory splices are very reliable! In our BASIC MAIN POWER diagram, we simply labeled this part "junction." When working with an original harness, which is in good condition, capacity of the wiring and this junction is adequate for alternators of moderate output. (Output as much as the Delco 12SI 78amp unit works fine, but REMOTE VOLTAGE SENSING must be properly wired.)However, as anyone can see, the junction is not friendly for addition of accessories-The factory never intended to add main power-up wires for electric radiator fans or other high current draw accessories to this junction.
The "junction" shown in the above photo is M.A.D.'s part
#CN-1. This is the most sensible, compact, friendly to work with junction in the industry. When up-grading to high powered alternators, a new heavy gauge cable can be routed from the alternator directly to the this junction. The factory dash area main power-up wire can be transferred to this junction. Many accessories can be added to the junction. The battery charging wire of optional gauge size can be routed from this junction to the battery. And fusible link wire short circuit protection can be installed at all outgoing circuits from the junction. When customizing the "BASIC MAIN POWER SYSTEM" shown in our diagram, this part#CN-1 is well suited for the job!
The OLD and the NEW,
both with REMOTE VOLTAGE-SENSING FEATURE
Back in the old days, when our Chevy Muscle Cars were new, technology was more primitive than today. The above photo shows a typical external voltage regulator used with most GM car alternator systems from 1963 thru 1972 models. Of the four terminals at the voltage regulator, one of the terminals served as the "voltage-sensing" terminal, and it was wired to the "main junction."