So my alternator took a dump on me and honestly im glad because I used the oppertunity to swap in an NA altnernator. Why do this you ask? Because the NB alternators are controlled through the ecu for voltage control. When you switch to an aftermarket stand alone ecu, this is a parameter that you have to tune and its a needless pain in the ***. NA alternators have a built in voltage control so by switching to one, you wont have to dick with it anymore. Itd does everything for you.
Jeremy at Flyin Miata gave me the directions and all I did was just change it a little so its a tad easier to understand. Mind you this is for an MSM!
Start by disconnecting your battery so you don't short something out. You'll also need the harness pigtail for the 94-97 alternator.
- The big white wire is the same for both units.
- There's a 2 wire plug in the 04 alternator with a grey wire, and a grey / red wire. Cut off the 04 plug, and splice the grey wire into the white / black wire of the 94-97 pigtail. Next splice the grey / red wire into the white / green wire of the early pigtail. Plug it in to the alternator when finished..
We have to move these wires, but we'll do it at the ECU plug (under the dash, by the steering column) where they're easier to get to.
-The grey / red wire goes to 3M at the factory ECU plug. Cut it off, and splice the harness side of the wire into a switched 12V source from the main relay.
-The grey wire goes to 4T at the factory ECU plug. Cut it off. Also cut off 3U (brown / red). Splice together the harness ends of 4T & 3U. The ecu will no longer be controlling anything with the alternator and you should now be seeing 13V continuous.
In the Hydra you don't really have to do anything. I turned the alt control off though just for the hell of it.