I bought a series 2- D15 from an estate and have
been trying to get it to charge.The battery is
connected positive ground.I've installed a new
voltage reg,had the generator checked,and still
no luck.

It was 12 volt positive ground.
--to test the generator, take off both wires on the treminals. Run a jumper wire from the "F" terminal to ground (+) on the frame. Get a volt meter and connect between the A and F terminals and then start tractor. It should jump to about 20 volts. Stop tractor and connect the generator leads to the A (G) and F terminals on the regulator. The B terminals is the output to the battery, normally thru the ampmeter first. Problem is ther is a 4th terminal on some regulators that connects to a second power source on the light switch, this may be your problem. If you have the correct regulator o.k., if you dont have the 4th terminal you will have an extra wire. Main thing to watch is that the regulator is properly grounded or it will not work. To polarize the unit, turn on the key and touch the regulator "A"(G) and "B" terminals so the regulator knows it is + ground. After you see the small spark, throw the small jumper away and start tractor and monitor the voltage. If you get stuck part way thru, send me a note. If you get no voltage at some part, then you can see if the generator or the reg is the problem. Again, chekc for proper ground on the regulator.

Well, I've got it charging,but I'm not any smarter
than a few days ago.Took the generator to a repair
shop,they said it was fine,you probably got the
wrong regulator.The one I got from Napa was a little different,but had the same connectors,(B,f,
G,.So I go home with another $50 voltage regulator,install it,and still nothing.This time
I notice if I ground the field terminal it will
charge.After a few hours of checking and rechecking everything I notice a small wire on
the field side of the regulator is only soldered
on one end and about a 1/16 away from where it was
supposed to be soldered.I soldered it together,
and now it works.Probably would have been just
as cheap to take it to the dealer in the first
place. Thanks, Guys.

I think it was, the D-19 is. Did you check the connections for corrosion?

I had the same thing except on a d-17. I found that the back of the dash was one big short circiut from the rust. If the back of the amp gauge if rusty like mine was then it won't charge. In fact it may even drain the battery and not even show up on the gauge.
Just a thought.
John