my sunrunner keeps killing alternators, not funny any more.

my alternator light lights up when the car is first turned to ignition on, then goes off, does not turn back on even if the alternotor stops charging. 

battery voltage is 12.2-12.5, tried with 2 different batteries, when  running, it slowly creeps from 12.5 to 13v.  if I leave the car run more than 20 seconds, the alt will fail, charging voltage drops to battery voltage

in about 5 seconds of running, the armature pulley gets super hot.  It does not do this if I remove the excitation and warning lamp plug.  Reconnecting either wire it jumps to 14.5V for about a second then drops to 12.5 and starts to creep up to 13v.

With an ammeter connected, I get about 18-20 amps of charge. 

I strongly suspect there is something wrong in the warning computer, but I cannot find it's location. 

Any ideas would be appreciated, I'm drawing a blank.  (does not happen often, I'm an electrical engineering technician)

I don't think your problem is in the warning computer.

The Engine Control Module (ECM) is usually located under the dash near the driver' side door in the vicinity of the fuse block.

go to Ack's FAQ (link in sig, below and do a search for engine and wiring and diagram.  That search will turn up two wiring diagrams for TracKicks, which might be helpful in understanding how the ECM works.  None of the diagrams show the charging system being connected to the ECM.

I think that you have either, a dud alternator replacement or a connection problem like a corroded connection or a connector that is not seating properly.

Hope this helps!