1990 Chevy Astro charging system

After replacing a bad altinater, it still isnt charging. theres aprox 15 volts coming out of the new alt. but not making it to the bat. i followed the wire from the alt, which went into a loom and to a multiple prong (10 or so) plug. i un bolted the plug and found heavy, black, gooey sludge in there. at first i thought it was the black plastic that its made of had melted, but its not. the stuff is tary? doesnt seem like there could be good cantact to those pins thru all that tar. What is that stuff? Is it some kind of cunductive material from the factory to prevent currosion? if that stuff is normal.... is there another link in the chain to the battery that my need checking or replacing? Thanx for any help you can give me,
Michael