I'm experiencing "engine run on".....Where should I place the diode ??? I have 2 wires from the alternator, one goes to the relay and the other one does not......

I'm experiencing "engine run on".....Where should I place the diode ??? I have 2 wires from the alternator, one goes to the relay and the other one does not......
Yr of car??? Does it have a external or internal charging system? If external, diode goes on brown wire (terminal 4) at voltage regulator. If internal, (or converted to internal) diode goes on wire to terminal 1 of alternator.

http://www.msdignition.com/pdf/6%20series/6series.pdf