97 impreza alternator problem

I have been experiencing some alternator symptoms. The alternator will not charge the battery when running. I have checked all the connections, fuses and belts which are fine in addition to replacing the battery after the car ran on the other battery, wearing it down. I have removed the alternator, and had it tested by two auto parts stores and an alternator and starter rebuild shop.

The alternator tests fine, but won't kick on, unless I short it out by grounding the hot lead on it. Then it runs fine for a while, but eventually won't kick on. I am going to replace it today, but I really don't think the alternator is the problem. It may be, but I am leaning towards the idea of having bad wires that are shorting out. Has anyone ever experienced this or have any suggestions?