The generator light is still on!
To recap:
1) Pulled generator, cleaned all contacts, installed new brushes.
2) Replaced regulator, though the connections aren't exactly as old one, it's the only one I could find.
3) Cleaned contact points (yes, bettery terminals as well) and replaced one generator lead that was questionable. Removed fuses (all are 30A; corroded but intact). Cleaned contact points on blocks and fuses and replaced; protected with dielectric goop.
4) Charged battery. It took charge with no issue and held it for more than a week idle. (It is a Diehard and appears fairly new, but no date on case. With state of the engine compartment, if it was more than a year old, it would show it!)
5) Checked output to battery with engine running... did not rise to 13+ after start but slowly rose from 12.06 to 12.64.
6) Checked wiring between regulator and generator for continuity. No problem.... resistance showed .002 on multitester.
7) Did the reciprocity test, both direct to battery and via regulator. Both ways spun the generator lustily.

What else can I check? I really don't get it... charging systems are usually pretty simple - it's either the regulator, battery, generator or a contact issue - but I think I've tested all the pieces with no obvious weak point.
HELP!
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1966 1800S in sunny Sandy Eggo

The generator in my 544 was acting the same way. No ability to charge but reciprocity test was fine and all interconnecting wires showed good continuity. George Downs suggested that an internal break in one of the field windings is probably the culprit and if I were adventurous enough it should be a fairly easy fix.

I needed the car back on the road quickly and so replaced the generator with a known working unit. The charging system is fine now. I saved the old generator for repair when a decent block of free time shows up.

Joe M

Generators won't put out anything like 14V at idle. Does it go up when you rev the motor?

If it's a new regulator, did you polarize it?

How exactly do you have it hooked up?

Nope, voltage does not change with revs.
Yep, followed the package insert instructions on "polarising". Never heard of it before and scared the bejeezus outta me, but did it. No change.
Unsure what you are asking... everything is mounted/connected in stock manner. If you mean the regulator, new one has a "61" terminal the old one didn't. Nothing is connected to it.
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1966 1800S in sunny Sandy Eggo