I've never heard of grounding the back case on an alternator until today. But the AlternatorMan says it very important. Anyone familiar with this need to ground the back half of an alternator case ??? Page down toward the bottom of the comments to see the AlteratorMan's comments. I've got my alternator all apart since it's only charging the battery at 11.8v to 13.5v and suspect the voltage regulator is bad. Everything else can be tested with an ohm meter and diode setting on your DMM, but the regulator needs special expensive test equipment. After running all the internal components thru the parts washer. .