Wont start changed starter just goes click - 1995 Nissan Sentra

I don't know what testing you have done, as far as wiring circuits? You can see the starter fuse in the diagram, not only check the fuse, check for voltage on the fuse circuit, use a test lite to check for voltage. At the starter motor itself, two voltage circuits, one hot all the time, the other goes hot when starter relay is energized. Check those voltage circuits. The starter motor grounds through engine block.
You can unplug starter relay, use proper jumper wire, between terminals 30 and 87, the starter motor should crank the engine. If you try that, make sure tranny is in park or neutral and parking brake is set.

sounds like you need a new distributor.... if you had a new water pump put in lately and didnt change the distributor that would be your main problem. The water pump in located in front of distributor, if that leaks it will short out and fry the distributor. Always change distributor when water pump goes.

you blow the main fuses

check battery is fully charged and all wires to battery and starter are correctly fitted

These cars did have problems with the antitheft system. When this system fails, the car "thinks" it is at risk for theft, and disables the starter. I would look into this before you change the starter. This link explains.

http://vatspasslockpasskeysecurityhelp.yolasite.com/

Did you try jupp starting the car?
Sounds like you have a low battery?

just one click or a rapid clicking???? a bad connection could cause this, or if its one big click and nothing happens, the starter solenoid may be bad. have someone tap on the stater while you hold the key in the start position. if it then starts, replace the starter. Buy quality parts, NOT from AZ if thats where you get parts.

Use a multimeter to test the main wire that goes to the starter that should have 12v all the time. The small wire that goes to solenoid should have 12v when you crank, which sounds like you are getting because the solenoid is what clicks. So it may just be a bad connection between the positive cable and the connection to the starter. Test everything with a multimeter then let me know and I will respond promptly.
Thanks,
Lee

look for the selenoyd conection or the starter Relay, also make sure that your battery terminals are clean, make sure You have connected the cable that goes to the battery to the right place

check the small connector at starter for voltage when cranking if ok try the hammer test if starts bad starter (ie) tapping starter with hammer while trying to start.