Alternator draining battery?

[dave`12]

I just completed a change over (long thread here) from external to internal regulated alternator. Well, I got sick right after, and didn't start the truck for several weeks. Dead battery when I tried.

I checked with a test light, and I have a battery drain that goes away (light goes out) when I unplug the 2 pin from the alternator. It's a 12si alternator.

Alternator definitely charging, and the ammeter in the dash is working properly. But I must have screwed something up, or got unlucky and got an alternator with a bad diode? Past history, I'm leaning towards "I screwed something up."

Does anyone know what likely is going on?

Thanx.