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AVR/Alternator Manual for 30 year old CAT 3408 Generator


I have a 30-40 year old CAT 3408 Generator Set. 

The problem is that it does not produce any voltage, i assume the issue is with the AVR/Diodes and would like to toruble shoot the issue but i dont have the manual for the alternator. 

The Generator Serial Number is B49BH7309.

I checked the diodes but they gave a .3V reading from both sides. To confirm if the issue was witht he diodes i checked the dioedes on another workign identical generator and the dioded gave the same value .3V from both sides.  Strange or NOT?!


Now i am planning to identify the wires going to the Rotor core from the AVR and separatley feed it off my 12V to see if this excitation generates any voltage. 

please recommend a course of action.