Both cases are similar. If you have a good ground between the case and body you should read close to 0 volts. If you have anything else, what you are measuring is the voltage drop through a poor ground connection(s). If you have a good connection between the alternator output stud and the starter relay stud, you should again read close to 0 volts. If you have anything else, what you are measuring is the voltage drop through a poor connection(s) on the positive side. You have to keep in mind that the system voltage the regulator is using for a 'sense' voltage is coming from the stud on the starter relay through the ignition switch.