Originally Posted by heintje23
And with the cable connected? Should it make a difference?
To test for an isolated ground. The B- cable going from the neg stud on the alternator must be disconnected. Then as mentioned by others, measure between stud and case.
If you leave the neg cable connected, a ground circuit is formed due to the neg of the battery
being connected to the engine
block, as well as the neg of the alternator.
An isolated alternator provides a low resistance path to the battery
, as long as the cable is sized for the proper voltage drop. It also eliminates circulating currents from the alternator to engine
block. High output alternators can cause electrolytic corrosion
at bearing surfaces, ans head
gaskets. That's why all high output alternators on boats should have an isolated ground.
Any alternator can be converted to isolated ground, with a little work.