I bought the alternator upgrade kit from MSA for my 1970 car. It's a 280ZX rebuilt alternator with a pre-built adapter that plugs into the wiring harness.

Not sure what's going on. here are my observations:

1. engine cranks, does not fire. Was running normally earlier today before swapping alternator.

2. After cranking a bit, I went to inspect. The white plug that fits into the wiring harness was hot. In a way that didn't need normal, and felt short-y.

3. disconnected battery

4. checked continuity between car ground and case and E post: ok.

5. reconnected battery for test: getting 12+ V at the B post

6. Didn't know what to check with the little 2-wire T plug.

7. no continuity between B and E post / B and casing.

8. On the adapter plug, with the stick-out-y bit at the bottom, the bottom pair of plus show continuity. The top 2 do not.

have the plug out and the battery disconnected until I know what's going on.

I tried this upgrade years ago and while I did not have the problems you are seeing I did have one issue: my ammeter was non-responsive/dead! I reversed course and opted for a reman 60A Hitachi externally regulated alternator and new voltage regulator from Rockauto. All is well.

On the alternator measure resistance to ground on both pins. You might have a short circuit in the alternator. New does not guarantee good.

One pin goes through the windings and the other measures output from the alternator. Both should have some resistance. I think that S should probably have infinite resistance. Not sure, but it should definitely not be low resistance to ground since it's connected directly to the battery. I would also measure resistance between BAT and E.

I would also turn the key on and see if the new white connector gets hot when it's disconnected. There could be a short inside the connector.

ZX alternator pinout.