DB 1210 charging system

I recently purchased a DB 1210 and it has been working great until yesterday. It acted as if it had a dead battery. I tested the fairly new battery with a digital VOM and found the voltage to be fine. I cleaned the battery terminals and the opposite connecting points at the starter and chassis ground with a wire brush and reassembled.

The tractor then started fine but the charging lite is on.
I let it run a while with my meter connected to the battery and watched the voltage steadily drop. I double checked the connections and they are good. I checked voltage at the alternator and found the larger gauge wire reads battery voltage obviously as they are connected at the starter. The lighter gauge wire reads only 2.14 volts.
So it is now not charging. Any help or ideas?

From your description the battery voltage at the rear of the alternator is the same as battery voltage as it should be, the charge light being on indicates the circuit between the ignition switch to the charge light to the alternator is correct, unplug the small wire and make sure the light goes out when it is disconnected. You could jump from the alternator output wire to where the small wire plugs in and see if that forces it to charge, if it does not increase the output to near 14V running at mid rpm range I would suspect a bad alternator, everything you posted points to that.

If it's the factory Lucas "dynamo" and it's bad (I think it is) then my suggestion is to convert to a Delco 10Si alternator. I went through 2 or 3 Lucas alternators on my 990 and finally gave it up. You have to fab a bracket for the Delco, but it's 100 times more reliable than the Lucas.

A few more thoughts on the reliability of Lucas electrical products-

The Lucas motto: "Get home before dark."
Lucas is the patent holder for the short circuit.
Lucas - Inventor of the first intermittent wiper.
Lucas - Inventor of the self-dimming headlamp.
The three position Lucas switch - Dim, Flicker and Off.
The Original Anti-Theft Device - Lucas Electrics.
>Lucas is an acronym for Loose Unsoldered Connections and Splices
Lucas systems actually uses AC current; it just has a random frequency.
"I have had a Lucas pacemaker for years and have never had any trou..."
If Lucas made guns, wars would not start.
A friend of mine told everybody he never had any electric problems with his Lucas equipment. Today he lives in the countryside, in a large manor with lots of friendly servants around him an an occasional ice cold shower...
Back in the 70's, Lucas decided to diversify its product line and began manufacturing vacuum cleaners. It was the only product they offered which did not suck.
Q: Why do the British drink warm beer? A: Because Lucas makes their refrigerators
Alexander Graham Bell invented the Telephone.Thomas Edison invented the Light Bulb. Joseph Lucas invented the Short Circuit.
Recommended procedure before taking on a repair of Lucas equipment: Check the position of the stars,kill a chicken and walk three times clockwise around your car chanting:" Oh mighty Prince of Darkness protect your unworthy servant.."

mE when i disconnect the small wire while running the charging light goes out. And after reconnecting I jumped from alternator output to the small wire connection and the alternator started charging and the light went out again.

Not sure i should have performed that test with the small wire plugged back in but it worked.

I suppose i will try to bypass that smaller wire from the alternator to the charging light with another piece of wire to see if maybe it is getting shorted or open somewhere.