I would check the back of the ammeter terminal for power first of all. Then test the other terminal of the ammeter for power. This other terminal "not the one coming from the starter" will pass the current to the B+ terminal on the key switch to give power to the truck. If you don't have power going from one terminal to the other on the ammeter then it's fried and you'll need another one.

Do some testing with a test light and see if you have power to the ammeter, the other side of the ammeter terminal and also down to the B+ terminal on the key switch.

Joe


Joe