I have a 1998 K2500 Silverado I use strictly as a hunting truck which i bought used a few years ago, Yesterday I hauled it down south to do some predator hunting. After unloading it and starting it few times and moving it around, we headed to the pasture. No Problems. I turned on the AC and the truck, immediate died. Tried to restart and battery was low and would not crank. Jumped the truck with my other truck and it fired right up. Removed jumper cable and volt meter on the dash read 9 volts. Called a friend and he brought a new ALT from Autozone which turned out to be the wrong one. He left to go get another one. While he was gone the rancher came buy and he has a 97 that the engine is locked up in. He let us take the ALT off it and after we put it on it would still not charge. My friend got back with the new one and we put it on, still no charge. I have a CHILTONS in the truck. We read and tested all the circuits, checked all the fuses, and looked at all the connections. Still nothing. Yes, the "L" wire is good to the alternator, it is supplying voltage to the ALT. Tested the large connection off the back of the ALT and getting battery voltage but it drops as the battery drains. Does the dashboard have a light as well as the gauge? If so the light does not work. Three alternators (original, one off the 97, and a new one) all bad???? When i get it off the trailer, I'm going to take the new one off and have it tested to make sure it works, but my suspicion it it's ok on the bench. Anyone have any ideas?