Non-charging help 89 Dakota

If the computer will not operate the alternator you can install a 70/ later Mopar external alternator. First, I would.......

Disconnect both field wires and isolate them "safely." Check both wires with the key "in run" and I believe one should have 12V

You can check the alternator alone (they work just like a 70's Mopar)
Check resistance between terminals. Should be very low. check resistance from both terminals to case. Should be infinity. The field is simply an electromagent

Ground either field with a jumper wire. Connect the other to a battery source and run engine. Voltage should rise, but be careful not to let it go above 16 or so.