2002 cav, 2.2. New battery, new alternator x 3. New ECM.

Here is the issue. When I first start the car I get 14 volts from the alternator for about 2 minutes, then the voltage drops to 12... After about 5-15 minutes it will re-engage the alternator and start charging at 14 volts again, but only momentarily...

I replaced 3 alternators now and all three did the same thing, so I started diagnosing, first checked the plug, and wires for damage, replaced the fusible link, replaced the battery, checked grounds/cleaned and reinstalled, replaced the ECM as I was getting a weak start signal on the red/grey wire plug for the alternator to start...

I'm out of ideas so if anyone could provide some direction on where to go next...

Everything was working fine till all of the sudden it wasn't... Like it flipped a switch and said I quit.

Ok I add a 10 gauge wire or bigger from the alternator to the pos. side of the battery and then add two grounds one from the battery to the engine and one from the battery to the body . leave the wiring the car has now , just add to it . see if this changes the way it charges .