I will add to the suggestions in the above post.
Ground the field at the generator and measure the voltage at the generator. If the voltage doesn't increase, you have a generator problem. If it is up, then see if it charging. If it is, try grounding the field at the regulator. If it then fails after passing ther previous test, there is a wiring problem between the generator and the regulator. If it passes but doesn't charge with the jumper off, there is a problem involving ther regulator.
