d 15 seriesII not charging.

It suddenly stopped charging. If it turns out to be the gen. would it be a good idea to change over to alternator? pros and cons...

Good Point!

I have mixed emotions about alternators and generators.  Typically if you leave the tractor original, ie don't add a lot of lights or electrical draw, I will rebuild the generator.  They are cheap and easy to rebuild if you get a kit.  It should have bearings and brushes, rarely to they need turned and the mica cut but some times they do.  Now this is on the generators with a regulator.  One big reason I like a generator on a tractor is alternators don't tolerate sitting in the weather very well as they are not sealed up.  Most of these tractors expose the alternator/generator to the elements.  If the hood covers the alternator well as later tractors and car do, or you have high loads, or store indoors all the time and never let it set out then I prefer an alternator.  Also cost is a big consideration. 

If you do good electrical work, converting a tractor from 6 volt to 12 volt is much cheaper to go with an delco 10si alternator than rewind a generator.  Hell its typically cheaper than having a shop rebuild a 12v generator and buying a new regulator.  Just please don't get a 1 wire alternator, their lousy and don't charge well at low rpms. 

The hooky set up that allis did with the light switch/cut out generators on the early tractors deserves an alternator as its to easy to run down or overcharge a battery if you are not paying attention.