Alternator Issues

[Mackay]

I am guilty of always observing but never really posting on the forums, but alas, my time has come to start a thread. I was hoping to get some ideas as to what could be the problem or what I could do to determine it.

The Info:

About two months ago, the car was running quite strangely, and would sometimes not start. After buying a new starter and taking the effort to install it, still no better. I finally realize it is missing a ground strap at the motor mount and all is well. This all occurred about 4 months after an engine swap.

About two weeks ago I was noticing that the defroster would randomly turn off when the blower was at full and other electronics were on. The ABS light would flicker and the headlights would vary in brightness. I checked the battery and it was 75% discharged. I bought a new battery and, presto change-o, everything is well and good. At the end of the next day after I installed the new battery, I was driving home with blower, headlights, defrost, and radio on. I parked at a gas station, and when I cam back out to start the car it lugged as if the battery was near death (which it was). So I turned off all the systems and limped home.

Troubleshooting:

When the key is in the run position but the engine is off, the charge light in the instrument cluster illuminates, but when the engine is running, the light is not lit. I have checked the voltage of the battery at idle, and it reads 13.5. The power from the battery to the B+ terminal reads 12.7 volts, same as the battery, but the smaller D+ terminal that runs through the charging light and the ignition switch reads ~.5. I purchased a brand new Bosch alternator that still does not charge the battery when installed. The voltage of the brand new alternator also reads ~.5 at the D+ terminal. I have exhaustively troubleshot the problem, trying all of the bentley procedures, as well as many ideas found online, in addition to the expansive Pelican Parts article and discussion on alternator issues. My next step is to pull the instrument cluster and check the charge bulb and relay, but I was wondering if anyone had any ideas or experience with issues of this nature?

Thank you,

Mackay