ford 2000 with duratech engine

i have owned this car 13 years. i have rebuilt the transmission. Other then that nothing
major. recently hard times been unemployed awhile. So when alternator went out was
able to get a cheap one from rock. i had local high school install alternator.

So here is the problem my car when running is fine, when i turnit off volt light and abs
light shine brightly. draining the battery. prior to new alternator this never happenned.
what could cause this. As it is now every time i stop have to unhook battery.