i have a 1987 amc jeep Cherokee 4 liter and on the passenger side inner fender there are 3 blue relay what are these relays for and what would cause 1 to click

 

Well i dont know about 3 blue relays. Mine were all black but here is what i think your talking about.

http://i25.tinypic.com/2s01y4z.jpg


I believe the clicking from the relays means that the relay connects the system but something is disconnecting it. Could be a ground?