Gauges and instuments

I have a 1998 Chrysler T/C Minivan. My wife broke down last week and said that the console (A/C, rear wiper, rear window heater lights) lights started flashing before she turned it off. The local parts store said it was the alternator. I replaced it and the battery and the problem did not go away. If I drive the vehicle for about 15-20 minutes, the console lights stop flashing but the battery light (on the dash) stays lit. My mechanic says that the new alternator is not charging because of the voltage regulator. I am being told that the computer has a bad voltage regulator in it and it is going to cost me 700.00 minimum to get it fixed. I have seen other posts with similar information - does anyone know what the problem is?