MY06TBSS

My son has a 97 chevy 1500 with thevortec 5.7...Last wk it stopped charging so we replaced the alternator....We have had the alterator checked and it is good but when you boost the truck off it starts and runs fine, the volt gaugedoes not move and when you take the cables off it will die and will not restart.....We are lost ..you would think it would have to be the alternator but like I said it has been checked and it is good.....Any help would be appreciated..

scss02

Sounds like the signal wire that tells the Alt to start charging is bad. But I would have the battery checked to be on the safe side