I typed this out... but before finishing I found the problem so here is the problem & solution.

I swapped a 2nd gen alternator into my 85 GSL. No rewiring needed for this particular year. Here is where it got funky... My original alternator would stay at about 11 volts until my RPMs hit 3K for the 1st time after starting and then it would jump to 12.5 and charge fine.

I bought the new alt for 5.24$ and put it in.

http://cgi.ebay.com/ebaymotors/ws/eB...MEWN:IT&ih=010

My voltage stayed at 11 volts permanently. I read that these alternators get fed a charge by one of the wires in the Tee connector that tells the alternator to start charging (commonly called the exciter or excitor or ...)

Checked for any charge coming out of the tee conector while the ignition key was turned and there was none. Checked my fuses and found that the fuse for the warning lights had blown. Traced the wires from the conector at the alternator back and found that it had been pinched and shorted. Ran new wires & loom. Replaced fuse and now the warning lights and alternator are working well 12.5 and greater from the start.

Still dont know why the original alternator got "excited" without the voltage... it got "excited" just by RPMs (kind of like I do). Makes more sense to me to do it by RPM... but the new alternator needed the voltage from the exciter.

And

If there's a fellow 1st gen 7 owner that needs a working 55amp replacement alternator but doesnt have it in the budget... you can have my original for the shipping cost or if you live in FL you can pick it up for free. PM me.

 

I tried an alt once that would kick in at mid RPM and stay charging. I discovered the T connector had fallen out. I pushed it back in and the alt behaved normally.

 

FWIW, your alternator should be approximately at 14v when charging.