If what you are asking is how to test the actual alternator housing to insure it has a ground
Then test the yellow/ white wire from it's connection at the alternator ("a" in the diagram) all the way back to the battery (where it finally winds up)
This can be done using "continuity"----basically this means you are sending out low voltage (like 1.5 volts) from the battery inside of the voltmeter. Down one of the leadsthen through whatever you want to test---then back up the other voltmeter leadthus completing the circuit
Disconnect the vehicle's battery---this will keep you from frying your meter by accident
The voltmeter is set on "ohms"--any ohm setting is fine for this application
If there is no circuit (or a break in in whatever you are testing) the meter reads "1" on a digital--or "0" on a analog (meter w/ a sweeping needle)
Suppose you are testing a 6 inch copper wire, placing a lead on each end of the wire "should have continuity" and a digital voltmeter will read "0" or "0.00"----on a analog voltmeter the needle will "max out". This means there is a complete circuit or the circuit has "continuity"
Sorta another variation to this is if there is resistance in the system---you will still have "continuity" except the voltmeter with give you a measurement of the resistance, instead of "0.00"----refining the exact resistance value is the reason for the different ohm settings on the voltmeter. Basically doing a "traditional continuity test" (looking for breaks) you need not worry with this.
So basically "1" means no continuity and "0.00 or a value" means the circuit got completed, and may or may not show some resistance----same goes for if the "needle has not moved"--moved partially or swept all the way across on a analog voltmeter
Some digital meters have a "beep" feature that can be used for continuity--this lets you "get on with it", without having to look at the meter face constantly.
This is useful if you are crammed under your dash---checking your fuses, without removing them, just by touching the little metal test port "windows" on the fuse itself, with both leads. Just remember, disconnect the car battery 1st!
So applying this in your question/ case
Test 1) one lead on alternator case, the other on your neg battery clamp (removed from battery)
Test 2) one lead on "a" at alternator connection, the other on pos battery clamp (removed from battery)
If this ain't what you are talking about---disregard all of this---and let fixitmr attempt to aid you!
I made some pics to help out my jeep cj guys---bear with them/ I made 'em a long while back, my 1st months having ever used a computer
Images (Click to enlarge)
Friday, January 20th, 2012 AT 4:22 PM