I recently purchased a 1986 XJS with the 5.3. The alternator is not charging. It appears to be the two wire alternator. The main wire to the starter was connected but the second bolt had nothing. I found the wire on the passenger side of the engine compartment. With the key on, the wire is getting 12 volts. When I attach that wire to the second bolt I then get no voltage reading...Grounding out??? With it attached, the dash battery light does go off, but still no charging. Does this sound correct? And does this confirm that the alternator is bad?