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Thread: 240z alternator upgrade (instructions w/ pictures)

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    Registered User Jarvo2's Avatar
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    Default 240z alternator upgrade (instructions w/ pictures)

    So while digging through my box of parts that the previous owner provided me, I ran across a brand new alternator, which ended up being a 280ZX internally regulated 60amp model. After upgrading to the Pertronix electronic ignition last year, I began to hear that the 240z's voltage regulator and 40amp alternator might not be powerful enough, so I investigated upgrading. All it cost me was the price of a diode ($2 @ Radioshack) as I had all of the other parts already.
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    After removing the voltage regulator I found out why its recommended to go with an internally regulated alternator -- look at how the backing plate has melted!
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    In order to eliminate the external voltage regulator I needed to create a jumper, including a diode to allow the car to turn off when the key is removed. Here is the best diagram I was able to find on the internet (thanks to the user who posted it here first!):
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    I ended up using a spare voltage regulator connector (and kept the somewhat working voltage regulator in one piece in case I ever needed to switch back). This connector then plugs in just like the voltage regulator would.

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    Once installed with the waterproof boot that I had laying around (which fit perfectly), I was able to tuck the jumper harness under the wires and it looks like its always been there.
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    Now that I've been driving on the new alternator without the external voltage regulator I can honestly say the car is running better than it probably did when it was new. This was a great upgrade and should be done by anyone having ignition or performance issues (I thought it was my carburetors, but all along it was electrical issues).
    Dave
    Windy City Z Club (Chicago)
    1972 240z, restoration in progress
    http://jarvas240z.blogspot.com

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    Registered User EuroDat's Avatar
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    Good write up Dave. It would be a good addition to the Technical Articles.
    Chas
    Chas
    5/77 280Z HLS30 403100 with some modifications
    Original colour: 305 Light Blue. The PO changed it to Red

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    Thanks. Dave Irwin just pointed out that this is only valid for 70-72 240z's as the 73 with an OEM electric fuel pump needs to be rewired to prevent battery drain.
    Dave
    Windy City Z Club (Chicago)
    1972 240z, restoration in progress
    http://jarvas240z.blogspot.com

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    Excellent!
    There is scarcely anything in the world that some man cannot make a little worse, and sell a little more cheaply.
    The person who buys on price alone is this man's lawful prey.


    John Ruskin (1819 - 1900)



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    Of course - Dave Irwin was selling the plugs pre-make, to anyone that wanted one - years ago here.

    FWIW,
    Carl B.

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    Walmart greeter Mikes Z car's Avatar
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    Terrific writeup. Great pictures too.
    Is the 280ZX alternator the best to use to switch to an internal regulator or is there another more widely used alternator (possibly a cheaper GM or whatever) that will work? I have read going with a GM alternator requires a bracket modification.
    Mike

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    Hi, I have done your swap in my 1973 240z. the swap worked, however my 12v yellow wire on the harness is melting??? What would cause this? Is it the starter wires? could it be multiple problems? how much money to take it to a shop if i dont get answers here? thanks for any input

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    Quote Originally Posted by Carl Beck View Post
    Of course - Dave Irwin was selling the plugs pre-make, to anyone that wanted one - years ago here.

    FWIW,
    Carl B.
    They are available through MSA: Motorsport! Alternator Upgrade Adaptor, 70-73 240Z - The Z Store! Nissan-Datsun 240Z-260Z-280Z-280ZX-300ZX(Z31/Z32)-350Z-370Z Parts.
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    Quote Originally Posted by Nobsz View Post
    Hi, I have done your swap in my 1973 240z. the swap worked, however my 12v yellow wire on the harness is melting??? What would cause this? Is it the starter wires? could it be multiple problems? how much money to take it to a shop if i dont get answers here? thanks for any input
    The wire is melting due to too much current. With no pictures, meter readings etc., it is difficult to diagnose the problem. It would not be due to the wires going from the battery to the starter. What is your ammeter reading when you're driving the car? How old is the battery?

    Maybe you should try the plug that MSA offers: Motorsport! Alternator Upgrade Adaptor, 70-73 240Z - The Z Store! Nissan-Datsun 240Z-260Z-280Z-280ZX-300ZX(Z31/Z32)-350Z-370Z Parts (Gee, this link looks familiar. )
    73 240Z
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    Quote Originally Posted by SteveJ View Post
    The wire is melting due to too much current. With no pictures, meter readings etc., it is difficult to diagnose the problem. It would not be due to the wires going from the battery to the starter. What is your ammeter reading when you're driving the car? How old is the battery?

    Maybe you should try the plug that MSA offers: Motorsport! Alternator Upgrade Adaptor, 70-73 240Z - The Z Store! Nissan-Datsun 240Z-260Z-280Z-280ZX-300ZX(Z31/Z32)-350Z-370Z Parts (Gee, this link looks familiar. )
    Yes, but we all learn the hard way. After a few hours of research, i found if i connect 1-5 and 2-3 on the connector, then i had 12 volts at the 2-3 connection... and that is where i put a diode. i found that the 5-6 connection doesnt work for 1973's, and the correct way is 1-5. however, when i connected this way, my voltage needle was on the middle line inside my cars' ampgauge. i dont think im getting the battery charging from the alternator.

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    Did you point the Diode the right way? If not, the alternator won't see the battery voltage.
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    Quote Originally Posted by SteveJ View Post
    Did you point the Diode the right way? If not, the alternator won't see the battery voltage.
    -yes, the silver line is facing the number 1 pin.
    (update) i disconnected the jumper plug and the voltage regulator. the car runs fine. what is going on? i think the car has been rewired.
    Last edited by Nobsz; 07-17-2013 at 01:14 PM.

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    Does your 73 have the Nissan factory-designed electric fuel pump retrofit? That could account for some of the wiring differences you are finding.
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    There is not a pump in my tank i have no gas tank in at the moment (the tank is rusted) And my fuel cell doesnt have a pump. I am only running the stock mechanical one, plus my numbers are too early. Its very confusing, as a deaf man use to own the car and i tried communicating as well as i could. I think he may have rewired the car because, with the regulator unplugged my car should still run with the key off right?

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    If I can find it (and have time and can remember to look), I have the added wiring harness that was used for the electric fuel pump. I can take a picture of it so you can see if you have one in your engine bay.
    73 240Z
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    I have this blog saved! I just did the alt upgrade! Seems better. However, I was checking amps and volts at the battery. volts were like 13.80 up to 14.09 i believe. anyways im not worried about that. the amps is what i am concerned about. I installed it and it was like 30~40 amps. then i went for a drive, the car died, i believe it was vapor lock, anyways got back and checked amps and it was like ~50. my question is, is that ok? also im gonna need some help locating the fuseable links on my car as i dont want to overload 40yr old fuseable links.

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    I'm glad my illustration is used for good write up :-)
    '75/280z

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    Quote Originally Posted by tamo3 View Post
    I'm glad my illustration is used for good write up :-)
    Thats a great illustration you made tamo3. Makes it very clear and simple to follow

    Chas
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    Original colour: 305 Light Blue. The PO changed it to Red

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    Im totally doing the oil switch so i can have an electrical fuel pump too! im just a little confused on the wiring from the relay. like 87 on the relay. the + wire. does that connect to the inline fuse behind the dash? and from the oil pressure switch, the wiring running from I. did you run that to an existing wire before the fuse or install one? I will have to physically go and look at this stuff soon, trying to get my tach to work and switch to the 280zx dizzy. Ive got some strange wiring going on there. hmp. again awesome write up and awesome illustrations for the ALT upgrade!

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    3ryce:

    For the relay, 87 is the power feed (once the 'system' is working i.e. oil pressure detected, ignition turned on, etc.) which then goes to the fuel pump itself through the green wire behind the radio. I just put a simple inline fuse for an added safety measure. Glad you guys are enjoying my write-ups!
    Dave
    Windy City Z Club (Chicago)
    1972 240z, restoration in progress
    http://jarvas240z.blogspot.com

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    Ok, i think i get it. my z actually has a working electric fuel pump with stock wiring, however what i dont like it when i turn it to acc the pump it on. I hope to fix that with the oil pressure switch. Yes i enjoy your blog very much! thanks again for doing that!

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