[R Bedell]

Would a bad ammeter cause this issue?

The current has to flow through the Amp meter. You should get a low resistance reading by checking with a DVM meter. Now this only checks continuity, and NOT movement. To check movement, you could move it to another know good source to check movement operation.

Wire the 128 EXACTLY as the Wiring Diagram indicates.

AS A TEST....
With all the devices disconnected from the Wiring Harness, you can take a DVM and connect the Black DVM lead to the Chassis Ground. With the Red DVM, you can test each individual wire in the harness. You have have NO readings (infinite resistance). If you do trace down the wire and repair/replace.