Seems like when I work on one thing on my old MB's I create other problems to chase down. When I turn the key on, the charging warning light comes on as it should. When I start the car the light goes off then begins to glow dimmly. The faster the engine speed the brighter the light gets. What would cause this? I'm good with mechanical stuff but not electric circuits.

A slipping Belt can be one of the Causes.

You can also remove the Voltage Regulator and see how long the Brushes are.

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84 300D, 82 Volvo 244Gl Diesel

I've got a tester. the alt/reg is working. I had the insturment cluster out. I'm thinking maybe I've got a problem there with something feeding back into the warning light or some other wiring/diode problem. If anyone has seen something similar let me know. Like I said, the warning light gets brighter as speed increases almost like it is registering the increased voltage not showing a lack of voltage.

One of our members posted this a long time ago:

AC voltage across battery
VAC across battery should be under 100 mV; excess AC voltage on the DC line means one or more of the rectifier diodes in the bridge are leaking or shorted. Such a problem is relatively rare but unfortunately means replacing the entire alternator.

Another:
ALTERNATOR DIODE check with volt meter
With your meter across the battery, on Volts DC, you should read 12.5 - 14VDC

If not, set your meter to Volts AC and you should have a reading of ~100mVAC.
If the VAC is too high, then look for a rectifying diode failure. If VAC is OK but the VDC is not correct, then the problem is with the voltage regulator.

At least 2 Members have said their Battery went Dead and thier Charging Light never lit up. When the pulled the Voltage Regulator they found one of the Brushes was worn too short.
Apparently the Brush issue can cause unpredictable results.

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84 300D, 82 Volvo 244Gl Diesel

14mv and 13.5 v The problem was in the insturment cluster. I had it out and something in the pc board was back feeding into the warning light. Fixed it and all is well now.