Nissan Repair: Nissan repair starting, neutral safety switch, nissan 240sx

Question
I own a 1989 nissan 240sx.  When I turn the key to start it there is a small plastic square thing next to the battery that clicks once and the starter doesn't crank.  I replaced the starter with one from a junkyard and cleaned the battery terminals but still no luck.  What could be the problem?

Answer
George,

Check to see if there is a neutral safety switch that is not working properly.  If yours is an automatic you should turn the key to start the car and move the shifter from park the neutral and back to see if the starter works.  If it does work intermittently then you know it is the neutral safety switch.  You can wire around it or get a new one.  If the car has a clutch make sure the clutch switch is working properly.  You can bridge the circit where the clutch switch presses against the stop, under the dash.  My bet is that it is one of these.