My 06 Expedition battery light popped on, I replaced the battery with a new one, I put a brand new alternator on it, and when I crank it it still won’t crank. When I boost it off and put the truck in drive in kills instantly, anyone might know what the problem is?

 

There could be a Mega fuse problem.
Check the wiring from the alternator output to the battery and the rest of the vehicle. There is a good possibility a heavy duty fuse in between the alt and battery or the rest of the vehicle may be open.preventing the alternator from charging the battery OR ,,,,,,,preventing sufficient power to the rest of the vehicle.. Insufficient power supply can cause engine shutdown

 

Ok I definitely will get that checked out thanks.