Are the ammeter readings higher then normal before the light comes "on"? The way this is presented, it suggest an overvoltage situation. (turning everything "off" resets the overvoltage relay).With a new regulator, this might point to high resistance, like a loose terminal, or even a corroded ground, Sometimes the big ground from the engine-to-airframe is overlooked. I would look real close at the big wire at the alternator, and the big wire under the panel where the power comes into the buss.

no financial intrest, but these guys are a huge resource for all alternator problems, and will talk on the phone. They sell a regulator with tattletail LED's & shorted field protection for SE Cessnas.

http://www.zeftronics.com/

Sounds like the overvoltage sensor to me. The sensor is located in the wiring bundle under the panel, close to the buss, on the pilot side. The sensor is about 1/2 inch in diameter and 3 inches long. There are three wires coming from it, orange, red and black.(Be sure these are all connected as I pulled my hair out recently due to a detached ground) This component is hard to find and I have found it to be a problem a lot. Looking at my schematic, I believe the P/N to be C593003-0101. I too have spent $$$ on alternators and regulators and found this to be a common problem. If the Master/Alternator switch is old that could also be suspect as these build up a resistance via oxides over time and will set off a signal as a high current draw. Find a GOOD electrician or Avionics guy as this will keep "throwing" parts and money at it to a minimum.