new altanator new battery no power to battery

I have a 2000 ford crown victoria  I recently had a
battery light come on and as I drive all my gauges
turn off and the car gets really  sluggish  so I took
my altanator off had it tested and it was bad. I
bought a new one from pep boys and the same
thing happened  so I had them run a voltage check  
they said battery is good but no power  was going
to the battery. So i returned  there  altanator and
bought a second one at a tutorial zone and had
them test it before  I put it on. The car drove
grateful for about  20 miles just before I got home
the battery light turned on. At this point  I think it's
a wire thing but when I put the new altanator in my
check engine  light went off. So I'm at a total  loss.