My brother has a 98 protege he just bought. The car supposedly came with a new battery, alternator, and starter. As of right now the cars alternator is bit cutting on. When it does start, the battery reads 14 volts but when you press the brakes the voltage begins to drop and the car dies. Yesterday my brother ran a wire from the alternator to the battery to see if there was a brake in the wires but her forgot to disconnect the old one so he sort of made a loop. This couldn't have been good for the system. He took it for a test drive and said the issue had been resolved. He then said later that day it died again and would not stay running. Thoughts?

 

The alternator is used to provide power to the engine. The battery is usually only there to get the car started. So loss of power during engine running would point me in the direction of the alternator. Engine wont continue running without it.

Engine mounts are something that are always overlooked and can cause issues to other components and given these cars are old, the one in the 99 are probably worn out so good idea to replace these as this could of wriggled a ground wire loose enough to cause you electrical issues.

Battery may show 14v but doesnt neccesarily mean it has enough Juice to power the starter if the alternator is faulty.