Bryan,
Your follow up post makes it sound 100% worse with the new regulator. It doesn't make sense for it to blow the fuse when touched to the frame. In fact the regulator should be grounded to the tractor when installed via regulator to tractor metal or fastening hardware. Make sure that what ever regulator you use is not painted as to obstruct a good ground. Also insure the mating surfaces are cleaned of paint and corrosion.
Internal to the regulator is the rectifier. This converts the AC to DC and also has a hand in causing the light to come on. Sounds like the rectifier is also toast.
It seems the new regulator is bad from stock. Could be a crappy build up by a sloppy tech. Most likely somebody fried it and somehow was able to return the bad device. Get rid of this thing.
Reinstall your original regulator for further testing.
What are the Cold Cranking Amps of the battery. Look for a new one if you have less than 850 on the label. Diesels being high compression need a lot of juice.
If the battery is not maintenance free then make sure the water levels are good. Especially before charging as described later on.
What is the condition of the belt? Is it tight enough? I usually go with about a quarter of an inch deflection when pressing on the belt. On these tractors the pulleys are close together. In a car withe the pulleys farther apart you could go half inch deflection.
Also, if the belt is too tight it will cause premature wear on everything. Stressing the pulleys and the belt.
Do you have a battery charger? If you do then put it on the battery at a low 2 amp charge and call it a night. Make sure the battery is removed from the tractor or at least make sure the cable's are disconnected and safely stowed.
The next day with the battery in the tractor check the voltage of the battery with out the terminals connected. Should be a good 12.4 volts or even slightly higher. Anything less is not a good battery after a night of 2 amp charge.
Now connect the terminals. With the key off and no electrical loads check the batt voltage again on the terminals, not the clamps. Make sure the voltage is holding good. Go get a drink and a snack. Go back and check the terminal voltage. If it is decreasing then something is drawing power. You will have to isolate and find it.
If the voltage is holding solid then start the tractor. If the tractor does not start and needs a jump then this implies the starting problem not the charging problem. This goes back to the new cables and sound connections.
It takes a very small trace of resistance on any part of the batt circuit to seem like a bad battery. Maybe nothing will happen or you will here a click.
Is the tractor running? Now with a meter check the terminal voltage again. Document it so you don't forget. Now check the voltage from the battery connectors, not the terminals. Document this also.
Ramp up the engine to high RPM. Please be careful at this point.
Recheck the voltages on the terminals and then the connectors. Document both readings.
Basic findings should be, with the engine running, higher voltage at the connectors, probably 14 or so. Checking the battery terminal voltage should also have an increase in voltage indicating it is being charged.
Other things to look at.
With the meter set at ohms, touch one probe to the negative batt terminal and the other to the frame. The best location would be at the location of the ground cable. But do no let it touch the cable connections, this would defeat the check. You should have strong continuity with no resistance. Depending on the make of the meter it may show in the neighborhood of 0.01 ohms. This will be ok as the we are actually getting slight resistance from the grounding cable that is completing the circuit.
Speaking of that cable, Ohm both ends and see what you get. Also ohm out the positive cable end to end. Document all of this.
If you are able to get this stuff done please add all of you documented voltage and ohm readings in your next post.
For your question about the schematic. The best I can suggest is either
this link to Messicks or what some people do, search ebay.
Also there was another thread started a little while ago about the flashers not working.
Here is that link. Even though it's for a B5200 it might shed some light
Thank you and good luck,
Scott