Nissan Repair: 1994 Pathifnder not starting, starter relay, crank

Question
I've had my truck for about 4 years now without a problem.  Suddenly last week, I would try to start the truck but all that happens is the ignition clicks then nothing.  My lights and radio still work, but no crank.  Then when I took it to my mechanic because I figured it was the starter, It turned over no problem.  I had my mechanic change the starter any way and the truck worked until I got it home.  When I tried it the next morning before going to work, same problem as before.  I was told it might be the ignition switch, but I hear the clicking as it tries to make contact.  Can you help please?  Could it be the starter relay?  Where is that located? I have tried to locate anything or anyone that can help me fix my truck as it's my only source of transportation getting to work.

Answer
Dwayne,

I would replace the starter relay.  Here is a link to rockauto.com

http://www.rockauto.com/catalog/raframecatalog.php?carcode=1211982&parttype=3804...

From what you stated this is the most common problem.  This is especially true since you replaced the starter already.