If the car is running what is the battery voltage? It should be 13-15 volts. If less than 12.6 it is not charging, which could certainly be the alternator. Check the belt and the wiring. My neighbor had a battery fail, and his car would only start with a jump. Try a new Motorcraft battery because it is made to fit correctly. Or, retest the existing battery after fully charging it with a battery charger. I hope it's not the alternator..
