Pontiac Repair: 1990 Pontiac Grand Am,,,,Electrical, jumper cables, fan engine

Question
Normal driving, turn on headlights, or heater fan, engine looses power.  Some-one replaced motor, with a 2.4 L, my guess is a bad ground or Alternator,,What do u think..

Answer
i tend t o agree that the power that is being pulled for the headlamp circut and opr heater is enough to rob the system from the normal power need ed to run, check charge sysyem first!  then chek battery, battery connections at the abttery then go to the grounds it should have a body ground as well as an engine ground, take a set of jumper cables and hook the neg side to the neg battery connection then take the other side and ground it to a good ground on the body and then start it and see if that changes anyhting if it does look for the bad ground