To clarify:

The first time this happened I had a very old battery in there. I would charge and recharge this battery before it finally died. The last time I charged it, I took it OUT of the truck and had it charged at Autozone. When I popped it back IN to the truck, no crank but everything else came on. Switched to my spare key and it cranked right up. As the battery was on it's last legs it finally died a few weeks later. Purchased a NEW battery. Took out the old and put in the new. Still using the spare key, I was able to fire it up with no problem. a few months later, during that week long heatwave, I was away so the truck sat in that searing heat all week. When I got back and tried to fire it up, click, click, click. Jumped it and still got click, click, click. Pulled it out, took it to AZ and let them charge it up. Put it back into the truck, went to start it with the spare key and was met with silence...AGAIN. Tried the original key, same silence.

As for the cluster test for voltage, can you walk me through that?