mechanicimnot

I have an 89 Chevy Scottsdale with 130k on it. As of right now it will not start. Turn of the key results in the "clicking" sound. I cleaned all the battery connections, tried jumping it but same results. I dropped the starter out of it thinking this was the issue (just changed the starter 6 months ago..had similar sound back then, that's why I thought this was the issue) Once on the ground I jumped the starter direct needless to say it engaged. I read somewhere else about a possible starter relay issue. First where is this relay located on this model & what is the best way to test the relay? Thanks in Advance!!

mechanicimnot

Also I have 2 more questions. 1 is when I use a volt meter to check the battery it will read 12Vdc the majority of the time however on occasion it will only read 3-6, which would be enough to run the lights etc. but not start the truck.
Also, there's 2 wires coming off the positive side. I assume the bigger 1 runs down straight to the starter. Where does the smaller cable run too? From up top it looks as though it runs down towards the starter as well. I know the starter has 2 wires on it but I thought the larger 1 was the positive from the battery & the smaller one was a negative from somewhere or is this the smaller wire thats also coming from the positive side of the battery. I know it can't be, why would there be 2 positives, but I figure ask now. Reason I'm asking about the cables is that it was suggested that I may have corrosion inside the cable & thus not getting 12Vdc to the starter.
I dunno, like it says, mechanic im not.
Thanks Again In Advance!!!!!!