The ammeter is between the rectifier and battery and so should show any charging current.
The rectifier is very easy to test with an ammeter set on measuring resistance. As per wiring diagram, there are 4 diodes to test in turn. To test each one, you need to measure its resistance with the ammeter leads connected one way round and then measure again with the leads switched the other way round. If the diode is working correctly, it should give a low resistance in one direction and a high resistance when connected the other way round. If you get a high resistance in both directions, it means the diode has blown. You need all four diodes to be working.
Also, did you disconnect the Zener diode when you switched to the power module. To roughly test the Zener, just repeat the test you did with the rectifier diodes.