The 200 ohm setting is the correct one. The reading for the first test should have been close to zero. The reading you got was >200. That means either you didn't have good contact on the testing points, the diode is bad, or something else is wrong with the wiring.

The way to confirm is to put the alternator back in, connect the battery, put the key in ON, and check for voltage to ground on the white/black wire. If you don't have voltage under those conditions, the alternator won't charge when running.

@SteveJ

Thanks for the information, I am going to go retest and make sure I got it right. I did check the diode plug with a meter, and it looked right.

I think I have another diode plug too, so will try that and see if anything changes. So to make sure I am right, I should have the positive on the ballast resistor and the negative on the alternator plug and should get close to "0"?

Am I correct that there is only one fusible link coming off the starter that feeds the car on the early z? For some reason in my brain I thought there were two..... not sure what that would be for........

Will get the alternator checked on Monday, since I have it out. Then reinstall........ THANKS so much for the information and quick response.......

Edited 13 hours ago13 hr by 70z4fun

Of course, there is one other possibility. I could have designed the test wrong. I dug out a diode that should be the same spec as the ones used in the plug and tested myself. I found my instructions were lacking.

You should re-test with the meter in diode testing mode.

You can leave the key in OFF, too. If you test from the ballast resistor to the white/black wire, you should get a result similar to this:

With the leads swapped, you should see this:

If you do the voltage test, you should see a little less than battery voltage as the diode causes a slight voltage drop.

Edited 12 hours ago12 hr by SteveJ

@SteveJ

Cool, will go try that later tonight..... Thanks for the information............

@SteveJ

Ok, tested it with the current diode plug

Here are the results:

With Positive going to ballast resistor:

With Negative going to ballast resistor

Will get the my current alternator checked out Monday, and I will check the one I had on before I got this one.
Did not find the other diode plug that I had as a spare, but will look for it on Monday. The "new" is slightly melted the white plastic on top

Well, the diode seems to check out. Test for voltage at the white/black wire with the key in ON when you get the alternator put back in.