Charging Indicator help

[KTA-Cummins]

I have an 83 300D turbo with a charging problem. It all started when i shut it off the other day and the charge light came on with the key off and wouldn't go out so I figured OK diode is shot so I disconnect battery to keep from running it down. Next day hook cables up sparks light comes on again so I say yep diode is bad. I start it up light goes out. Drive it to work turn key off light stays off. I disconnect battery no sparks?? I say huh fixed itself??? Oh No. I start it up to go home an now here is my current problem. Charge light is on dim when idling, gets brighter with rpms. I said OK maybe the regulator is dying so I check voltage it is a little low at 12.6. I bought a new regulator and put it in and the problem is the same except now when I rev it up the charge light gets REAL bright. I checked my volts now and at idle I am getting 13.5 and at 4000 I get 17volts!!!! HELP what is wrong with my trusty friend??? I want to get it fixed before it dies on me so far 4 days with it screwed up and everything electrical still seems to be working fine?
I did some more testing and it gets weirder. If I turn it off and start it back it charges around 13-14.5 across the whole rpm range- for awhile- after about 5 minutes the voltage starts to rise to the 17 volts previously mentioned. If I turn it off and start it back it charges fine again???? I am pretty sure that if I put my old regulator back my over charging problem will be gone as I think I must have gotten a bad new regulator, but the brighter with increasing volts indicator is still puzzling. I thought maybe the key switch would be messed up and grounding in reverse, but wouldn't that make all the warning lamps light up?

HELP!!!
Thanks Brian

[Moneypit SEL]

Sounds like you might have a failed diode in the alternator after all. Ideally, you could look at the alternator waveform with an oscilliscope and the voltage ripple would be obvious. You can still check with a multimeter, though. Set the meter to measure AC voltage and Range to about 2 volts. Measure with the positive lead at the + side of the battery, and the - lead to negative. The lower the AC voltage, the better. Anything over about 0.3 vAC spells trouble.