I have a 1999 Chevy 4 wheel drive blazer.... One day it just wouldn't crank. We have 2 different battery chargers at home and they will charge the battery but it still wont crank, even trying to jumpstart it wont work but when we take it to our machanic friend they hook it up to their big charger and 30 minutes later it cranks right up but once I cut it off it won't crank back up.... I don't know if this is important but before I try to park ill put it in park and it will start to roll like its not in park but when we first get it to crank it doesn't do that. We checked all the fuses under the hood and they're fine. We just can't seem to figure it out. Please help!