Sorry to read that your adventure is turning into an ordeal...
You mention that
The batteries have a diode system and it seems that thge diodes click off most the time either draining the batteries or not charging at all of sometimes they will infact charge the batteries but for only a short time but not enough to top them off.
I don't want to sound difficult but there are a couple of things that need to be clarified so that I can hazard a guess; 1. batteries do not have diodes. Batteries are connected to the Alternator, which does have diodes. Batteries are sometimes connected to a battery isolation diodes, which enables you to charge seperate battery banks independently 2. Diodes do not "click." Diodes are semi-conductor devices, and have no moving parts. Did you mean to say that you have a Battery Paralleling Relay?
Assuming that you do not have a relay, your second observation
My tachometer stops reading rpm when the batteries are not charging
helps identify the situation. The tachometer in a diesel is frequently connected to the alternator. I believe that you may have a fault in the field winding circuit of the alternator, or possibly a bad voltage regulator. Does the tachometer work when you start the engine, and then unexpectedly stop working, or does it not work at all?
I would carefully check the alternator, looking for a disconnected (ABYC Standard would be Brown) wire that sets the field in the alternator. The terminal on the alternator is probably marked "1," "F," "DF" or "FLD." This wire may either go to the voltage regulator, a pressure switch on the engine block, or to the key switch. A "quick and dirty" test would be to disconnect the negative (ground - should have a black or yellow wire) lead from a 12V cabin light and attach one end of a length of wire to it, start the engine, and touch the other end from that wire to the alternator feild winding. If the alternator starts charging, then you have narrowed down the problem to one of the switches that I mentioned above.
If you have shut off the key switch before pulling the engine stop lever, or before the engine has stopped turning, it is likely that you have blown the diodes in the alternator. These diodes convert from AC (produced in the alternator) to DC. To test them you will need a multi-meter.