The voltage drop test I outlined earlier in this thread should help you pinpoint your fault. Follow the wires from the alternator, where do they go? If they run to the starter then you will need to test for voltage drop between battery positive and the alternator connection. Should you have a high voltage reading then suspect the connection at the starter motor.

If the wires from your alternator run to a "Terminal Block" then this will be your test point. Test between battery positive and the terminal block, if you have a high voltage reading then suspect dirty or loose connections at this block.

In my many years working on 123 cars I have yet to replace an alternator harness due to excess line resistance! Loose and or poor conections repaired, yes. Harness replacement, no, then again there is always a first.