Youve got a 3 pin plug on the alt,have you each wire used? looking at the alternator the top pin will be an "S" terminal,bottom left "IG" terminal and bottom right "L" terminal. S should be constant 12v,IG should be ignition switched 12v and l should go the the bulb in the cluster,where the opposite side of the bulb will have an ignition switched 12v also. S tells the regulator what state of charge the battery is in,IG switches on the regulator and L is just a way of telling you theres a problem with your charging,older alts used the l terminal as a means of exciting the coils to begin charging but new alts do it electronically. Thus you dnt need the light to have the alt charging.