Non-charging help 89 Dakota

to me (no computer controlled car expert) it sounds like the computer is expecting a signal from something to tell the computer that the engine is running and start regulating the alternator output. My guess, there is a crank position sensor that is not hooked up, so the computer does not know the engine is running.

as for fix... what 67 dart 273 said
That is a point. If the engine was getting RPM triggers the tach should work "I think."