How to hook up ammeter?

[Knoxville71shortbed]

I need some help. I'm installing under-dash gauges, and have run into a problem with the ammeter. According to the instructions, it said to remove the wire running from the positive battery post to the junction block on the left inner fender. Then it said to hook one of the wires from the ammeter to the junction box, where I just removed the battery wire. Lastly, it said to attach the other ammeter wire to the wire that was removed from the junction block (which goes to the positive battery post). I did this, and when I attempted to start the truck, it wouldn't crank at all. To double check myself, I hooked everything back as before (disconnecting the ammeter), and the truck started perfectly, as usual. I then tried again to hook up the ammeter (same connections as before), and got the same results (would not crank). What am I missing here? Is there another way to hook up an ammeter? I need some advice here. Thanks.