I have an 85 Z28, 305 TPI, how many wires should be coming from the alternator, i have the two prong plug and the only wire on it is just a short jumper back to the alternator, i found another black wire that the only place it looks like it can plug in is on the other side of that two prong plug, any info?

 

ALT plug should only have two wires

Red 12v from some constant hot source. Either power distribution block or a lead off the battery cable side of the starter
Alt will not charge without this wire

Brown alt gauge which goes thru the C100 connector
Not required to run

 

The red wire is the voltage regulator reference source and is customarily jumped over to the alternator output which is connected to the battery via the starter.

If the brown wire isn't hooked up the alternator rectifier won't get excited at low RPM. It is hooked up to the gauge and battery warning light normally. If you hook it straight to battery power it will fry the rectifier in short order. It needs a bulb or resistor between it and a keyed (ignition on) power source.