Need a little help with 1981 C10 battery drainage

[jcloud6]

Need some help with determining whether my battery drainage is in the alternator, starter, or the wire harness leading from the bus-bar to these components.

I isolated the problem using a test light conected from the negative cable to the negative battery post.

when I dis-connect the starter wire from the Bus-Bar and completely dis-connect the wires from the alternator the test light goes off.

If I'm not mistaken the battery power flows to the starter selnoid, alternator and the bus-bar which power the ignition and all other components.

I took alternator to Autozone and had it tested, they told me the alternator pass the three test they ran on it.

With the alternator passing the test, is it safe to assume the drainage is in the starter selnoid or wiring harness from the bus-bar.

How do I determine which of these components are causing the drainage??

Any help can give will greatly appreciated

Jonas