Actually the cable you are referring to was from a temp sensor below battery. This was used on 85-86 models. The idea was to give the most accurate voltage regulation that would charge battery while causing the least amount of electrolyte loss. The concept is good but the sensors were prone to absorption of the electrolyte which altered the level of signal back to voltage regulator and the charge voltage might actually go too high and cause excess electrolyte loss. OOPS! Never mind! This was dropped on 87 models (actually during 86 production the sensor was deleted and the regulator had a blank sealed plug over the connector.