pull the green wire female connector off of the field terminal & ground the male field terminal for 5 seconds (fast idle)/lights/acc off & see if you have magnetic pull or the voltmeter rises. If so the alt is good. If not, check the brushes/brush holders & if they look OK then yes the alt is bad. Get a 78 amp alt for an 85 M body (perfect fit/better alt), price should be similar & even if higher I would still go with it. If the alt IS good holler back & we'll continue on. EDIT the screwdriver test is at the rear center & has to be running as the alt ain't charging when not rotating even if it has field current to it (key on/not running). MORE EDIT My parts house just quoted me $42.75 out the door exchange for a rebuilt 78 amper for an 85 Chrysler