I have a '72 H/O with a bone stock 455, that just started killing the battery after sitting overnight. The battery has been tested good, so I went thru various points on the wiring harness with an ammeter and found there is a 2.5A drain on the battery that disappears when I unplug the blu/wht connector from the alternator. It has a 63amp unit with an internal rectifier.
Any suggestions as to a next best step? I want to keep the original alt for authenticity's sake of course! Thx for any advice!

 

I had a similar problem with a Nova, and replaced the diode trio. It solved the problem in that case, but I have no idea why, lol!

 

Me thinks that it is time for a rebuild on the Alt.

 

Yes, a shorted diode will cause a continuous drain on the battery.

 

Speaking from experience, most battery drains come from the regulator or the alternator. My local Advance and AutoZone can test both free. I normally remove both and test.