changed my 55 to 12 volt.car wasnt running when i got it.2 new regulators 2 gen,later it shows about 12.5 max then will drop to 12.just enough to keep the light out.im at wits end hate to go to an alt,even if i did i have a feeling it still wouldnt charge

Save yourself some time, money and aggravation and change to an alternator.  Even if you found some old auto electric mechanic still alive to fix your generator, what would you have?  There are kits that make this an easy install.  You don't have to worry about old voltage regulators, there is nothing to adjust and your battery will stay charged.  My Tbird has a Casco alternator kit and 1957 HD TBird Battery. One of the best upgrades I have done to my car.

I assume  you went with a new battery when you made the change, but it's possible it may have some shorted cells.  This increases the amperage flow into the battery with a resulting drop in voltage.  The charging light works on voltage not amperage.  
Put a battery charger on it and see what level of amperage and voltage it will accept, or if you have an old ammeter lying around, hook it into the generator output circuit to check amperage.  Also check the belt tension and length.  It really sounds like a belt or pulley size problem.
Or, as Florida Phil says, this may be the time to switch to an alternator.
If you want to stay with the generator, as an old automotive electrical mechanic, I am pretty sure we can get to the bottom the problem.
The two things you would need would be an ammeter (an old under dash accessory ammeter would be fine) and a voltmeter or multimeter.  








     

I fought my generator and regulator for a long time. Never could get a regulator to work with the generator. Finally went to the Powermaster alternator that looks like a generator. Zero problems for a couple of years now.  

thats where im at.2 used and 3 new.regulators later.starting to think alternator.but i cant believe i cant overcome this.all my life ive never run into this before.

All connections need to be clean. Measure resistance across each connection and across several, must be very low, less than 1 ohm preferably.
Was the Field Terminal of the Generator Grounded ? (short the A to F terminals while working) !! Be sure the Regulator is not a Delco Remy with double contact voltage control, points will burn !!
Voltage Regulator has a good ground ?


1936 Ford 3W Coupe : 56 T-Bird 312, 47 Packard 3 speed, 40 juice brakes.
1968 Merc Cyclone FB GT 390, Getting a better front clip!
1977 Ford F-250 Supercab RWD Explorer Long box.
1976 Chev Camaro RS LT
Future rebuild : 1949 Ford F-1

fixed.friends up the road run a garage bring it up and well have a look.i knew their wasnt much they could do.i left an hour later with an alternator.14.9.

Glad it worked out one way or another. The powermaster I bought allowed the “I-did-it-light”  to remain in the circuit which is a plus for me. The CASCO  system I bought for a T-Bird and modified for a passenger car had to go back in its box when I added the AC unit. It could not fit the Vintage Air mount. 

56 Vic, B'Ville 200 MPH Club Member, So Cal.

Take the generator off and put new brushes in it.