Start the car and check the voltage at the back of the alternator - if it is 14 volts or so - follow the wire - you will see where it is not hooked up. If you find the other end of the wire and it is hooked up - check the voltage there - if it is the same as at the alternator - then the wire is good - if it is lower - the wire is bad. If you start the car and the voltage at the alternator is under 13 volts - get a new diode brush pak first and try it - works 80% of the time. Hope this helps
Morris