Charging Indicator help
 

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

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.