Alternator

[NCheek]

I was installing a gauge kit on my dad's truck today ('99 F-250 4x4, 7.3, Auto), and after I finished up, I reconnected the batteries and cranked her up. The cranking was definitely longer and more labored than usual, but the truck fired off anyway, and sounded fine, except the battery light did not turn off after its initial period. I checked the voltage at the batteries, and at the alternator, and only got about 12.3-12.5 volts whole running...

What is the procedure to make the alternator go full field that I can check if it is able to charge, or if it is the root problem? I took the plug off of the alternator, and the two outer pins were the same voltage as the battery, while the center of the three pins showed no voltage.

Any help or possible diagnoses would be greatly appreciated.

 

[yoslick]

Need about 1100-1200 rpm for max output on the alternator minimum, sounds like somethings not making connection or by chance yours took a dump....

 

[NCheek]

Went to crank it this morning, and it was a no go. Batteries had 12v before cranking, GPs brought it down to 8v, and then when I turned the key, nothing. I jumped it off with the IDI, so I guess it's off to O'reilly's to get a new alt