1998 Ford Ranger Alternator bad

My Ford Ranger had the battery light on and the voltage meter show low charge. I took it to Sears because that is where I got the battery. They said the battery was bad and replaced it, new battery. When they tested to see if that fixed it, everything was the same. They said I had a bad alternator was bad. I drove it home because I can change the part.
Went to AutoZone Got a new alternator and installed it. Same problem as before, no change. I have checked all of the conections and wires and found no problems. SO, I took the alternatior back to AZ and they gave me a new one. Came home, installed it. Same result, Battery light on and volt meter on the low side. What am I missing. I so like PNP auto parts.