my GEN light stays on. van will not charge on 1996 Dodge Ram Van 2500

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the GEN light is on and the lights get dimmer, and the van stops. Had the computer replaced. Now the GEN light is still on, and also alot of lights on the dash are on too, and the van loses power and stops. Also the GEN had been replaced. Battery cables OK
(2) Answers
Is the ALTERNATOR charging , was the battery FULLY charged before putting the new alternator on and burning it up? Where all the codes that were set because of low voltage cleared? What was the reason for PCM replacement?