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Old 10-24-2009, 02:21 PM
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Tracking Down a Short

I've experienced a slow battery drain for a while and tracked it down by inserting a piezo buzzer between the positive terminal of the battery (which is located in the trunk) and the red battery cable. Then I pulled fuses to see where the short might be. I'm using a Ron Francis harness.

It turns out it's the #2 terminal of the AC/Delco 12SI 94 amp alternator. The alternator is wired: stud to starter via #8 wire and then to battery in trunk, can't remeber the guage, but it's one size bigger than the charts recommended; #1 to switched B+ in ignition circuit; #2 to bus that feeds the fuseblock for voltage sensing (I added this a while back because the battery is in the trunk and the BBC needs adequate voltage and current for the starter ).

Should I be hearing a tone (which means that current is flowing) at the #2 terminal?

Added: I did find this: "Another is that the field connection inside the alternator can allow a small current draw while the vehicle is not running, and this can cause a dead battery if the car is stored for a period of time." at

So do I have it wired wrong? The # 1 wire was wired per the RF instructions; I added the #2 wire for voltage sensing.


Last edited by hduff; 10-24-2009 at 02:29 PM. Reason: added info
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Old 10-30-2009, 03:01 AM
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Pin number 2 does eventually go through a resistor network to ground inside the internal regulator, but per the attached doc, the drain is "negligible". I've found this doc to be a pretty good source on the different types. Image 010 looks like you describe your hookup.
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Old 10-30-2009, 04:34 AM
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Great link that was a big help. Thanks so much for the reply.
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