Nissan Repair: 94 Altima Alternator Problem, neutral safety switch, nissan altima

Question
  I have a 1994 Nissan Altima which had a faulty alternator and battery. Both were replaced a few weeks ago. The car ran fine for a while, but then suddenly would not start. When the ignition is turned, nothing happens. No click, no attempt to crank, nothing. The battery is charged and all internal electronics (radio, lights, etc.) are working.
  The strange thing is, I can sometimes get the car to start by holding the ignition in the start position and tapping the alternator with a hammer. After doing this, the car will usually start normally a few times, then revert back to to not starting and I will have to tap the alternator again. Today, however, the hammer method would not work and the car would not start at all.
  My guess is that the new (refurbished) alternator is bad and I need another one. It is under warranty, but I will have to pay to have the new one installed again. Is it possible that there is another problem and that it is not a bad alternator?

Thanks.

Answer
Eric,

If the car has a charge and will not start I would try to start it while running the shifter from part to neutral.  It sounds like the neutral safety switch is defective.  If this does not work you could wire around the switch or the easy way to see if it is the starter or the neutral safety switch is to run a wire from the positive side of the battery to the little terminal on the starter.  If the starter turns over the car it is the neutral safety switch.  If it does not turn over replace the starter.