240SX Alternator Swap

[venom42]

I am starting this thread because I searched and searched for info on this topic, and had to use bits and pieces gathered from several sources to put it all together.

I got an alternator from a 1995 240SX SE from a Junkyard for $40 shipped (www.car-part.com). I chose this one because it as close to "bolt on" as it gets for the power, cranks out 90A, is internally regulated, and has an internal fan.

1. You need to make a pigtail for the harness that your external voltage regulator plugs into. I happened to have an old one lying around, so I did not have to cut the wires from the "good" one on my car. Follow the directions on the ZCar Creations page located here. My car is a '75, so I did not have to worry about "run-on," but if you have a 240Z or 260Z you should also note what they say about splicing in the diode or whatever.

2. The plug on the 240SX alternator is very different than the "T" connector on our cars. The wire closest the the alternator output ("+") terminal needs voltage from the battery, which is the horizontal part of your "T" connector, if you look at it as a capital "T" (I hope that makes sense). The other wire goes to the vertical part of your "T" connector. The alternator that I got had the plug still on it, so I just soldered spade connectors onto the wires and plugged them into my "T" connector (I also put shrink wrap around them to make it look nice). If you do not have the plug, then you need to make some jumpers to connect to the plug terminals and your "T" connector.

3. You need to flip your adjusting arm around. Simply take it off, turn it over, and bolt it back on. I also had to use a shorter bolt for the adjusting ear, but I dont think the one that was there before is the original, so you may not have to worry about that.

4. You need a longer front mounting bolt. I happened to have one that was perfect. Otherwise, go to Home Depot with the one from your car (you could even pull one out in the parking lot :classic: ). You need one about 1/2" longer.

5. You need to get some spacers for the mounting ears. I dug through all of the metal and nylon spacers in the Hardware section at Home Depot and only found one that I thought would work. It turned out to be perfect. It is a nylon spacer that says: 27/64" long 29/64" OD X 324" ID on the bag. The sku# is 030699872787. It goes on the inside of the front mounting ear, which is thicker than the one on your stock alternator. Then you need to tap out the little metal spacers from your stock alternator. One goes in the outside of the front ear, and the other goes in the rear ear.

6. The 240SX alternator has a serpentine pulley on it. You need to swap it to a v-belt pulley. The one from your stock alternator will NOT work. Your local auto electric shop should be able to do it for you. I took mine to Georgia Auto Electric in Smyrna (for those of you that live around Atlanta). They swapped it for me for $10. If you have a pulley that will work, and the spacer to go underneath it, you can swap it yourself with an impact wrench.

7. The ring terminal that connects to the charge terminal on the stock alternator is too small to go over the terminal on the new alternator. You can cut yours off and splice on a new one (I would also add about 1" to the wire if I went this route). I did not want to cut my stock harness, so I cut the terminal in the middle with some wire snips, and spread it open enough to go over the new terminal. I also chose to run an additional 8ga wire directly from the charge ("+") terminal of the alternator to the positive terminal on my battery. It may not be necessary, I just wanted to take some of the load off my stock wiring, especially considering the output of the new alternator.

Thats it. Bolt it up. Plug your new pigtail into the car side of the voltage regulator harness (I left my VR on the car and taped up the plug on case I ever decided to go back to stock). Plug your new spade terminals into the "T" connector. Bolt on your terminal connections and ground (and that little diode thingy that was bolted to your ground terminal on your stock alternator). Take it for a spin.

My lights were brighter, and my idle was correct for the first time since I built the engine (it had been idling high most of the time). Best of all, I can finally put in my 16" fan to stop my overheating problem when the car sits at idle (there is a 14" on there now). It charged my battery from 11.5v to 12.4v in the time it took me to pull the car out of the garage.

[CoastGuardZ]

Mike,

Outstanding write-up! This is VERY good info and in fact you have inspired me to take this project on while my Z is in winter lay-up. Worth mentioning... I noticed on the Z Car Creations page that you linked to, that they noted for 240Z and 260Z to install a diode to prevent run on. Thanks for the time you spent gathering up the info and placing it into one solid article, It will save many of us a lot of time.

Nate

[Arne]

Great info. Admins, this thread should be moved to Tech Articles, it's clearly that type of post.

Also, the alternator adapter developed by myself and Dave Irwin - and still available from Dave - would also work for 240Zs with this swap.

[venom42]

Turns out the idle being correct was a fluke. It is back to normal today (it idles anywhere between 1100 RPM - where I have it set, to 2100 RPM, just depending on how it feels that day). However, this swap is still very worthwhile. Just for grins I ran the heat, wipers, lights, and stereo on the way to work today (the cooling fan was also running), and it handled it with no problem. On my stock alternator this would drain the battery. I plan on sticking my 16" fan on over the next couple of days too, but I dont think it will make a bit of difference. This thing kicks out enough juice that I am no longer concerned about adding an aftermarket ignition either. It looks better too (internal fan).

Thanks for the positive feedback guys. I just thought it would be nice to have all the info in one place, rather than having to gather it from several sources.