Not necessarily...but, normally, it would be like a tenth of a volt, or less if that wire is good.
Hook everything up it should be.
Start the engine. Read the voltage at the alternator. In other words, put the red probe on the back of the alternator and the black probe on the alternator housing or the engine. What does the voltage read? Is it over 13 as it should be when charging? If it is over 13, then move the red probe over to the positive terminal of the battery. Is the voltage showing over 13?
If not, then the problem is wire from the alternator to the battery. It has a connector inside it about a foot from the battery that sometimes goes high resistance.
If there was not 13+ volts at the back of the alternator in the first measurement above, then turn the engine off. Then turn the key back to "run" so the check engine lite is ON. Is the volt light on the left side also ON? If it is not, then your problem is in the dash light circuit. (normally, this is the first thing you check before doing anything

)
Scanmaster voltage being low does not always mean the alternator is not charging, but, can be another problem.