Power Problem Alternator or wireing

[moishloi]

I have been going at this for 3 days straight. I'm in need of my truck, but I have no one who can help me so I am coming to you guys.
I have a 1988 chevy suburban v20 with a 350 5.7 liter engine. I have installed a working 105 amp alternator as the previous one went out. I also found the + cord going from starter and alternator to battery was eroded I replaced that as well.
I have 2 batteries for some reason.

I have been going at this for the past few days. And My problem is still not solved.
The problem is that when started the car wont go to 14volts as it used to. Now it sits at 12 and eventually it will strain alternator and probably kill it. I don't really know what else to do or check. Please help

 

[zora]

with the engine off and key in the on position what voltage reading do you get at the large single red wire on the back of the alternator and the red wire in the plug and the smaller wire next to it? If you get zero voltage on any of those wires that wire is your problem. Did you have the "new" alternator bench tested to make sure it is working?

 

[VanGo]

I'd test it as mentioned, but first I'd make sure that the part numbers match.