So, I drive a 96 2500 and like most have the "sticky starter" issue. The starter stuck the other night and didn't release as fast as it normally does when this happens. So after listening to the metal on metal for 2 minutes I unplugged the FSS and it stopped running.  Plugged it back in and cranked a few times but wouldn't start. Popped the hood after bumping the starter and manually pushed the FSS up. The hold wire did its job and I went on like this for a couple of days. My buddy noticed that the blue wire that has the internal fuse connected to the driverside battery was corroded, so we put a new connector on it. Tried to start it and the wire as well as the FSS got very hot very fast. Couple of hours later went outside to drive it home and it started right up, no hot wires no hot solenoid nothing. Here's my issue, something is draining my battery, the truck sat all of saturday and Sunday and this morning didnt want to crank. I'm good with wrenches, not so good with multimeters. Any ideas?

Sounds like the solenoid relay is sticking on.

The one on the firewall?

If it's not relay it maybe contacts and plunger inside the starter sticking somehow, but does sound like a relay.  If you can pull it to then you can rebuild it with Larry b kit, cheap and easy. Probably time anyway. 

What's FSS?

 

Yeah Larry B's kit