Too Good to Be True? – 125 Amp Bolt in Alternator @ Datsun Store

[RS02]

I found a website that manufactures brand new GM alternators that's somewhat customizable. I ordered one with the lower mounting tab thinner(1 inch instead of 2) they have some options for pulleys and amp range. I'll update once the unit is installed.


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[Matthew Abate]

Post 203, Page 9 of the thread (wow that thread is getting big...!)

Oh yeah! I have this saved in my how-to bookmarks.

[sweatybetty]

i guess my question is this

how big of an alternator do you really need?

big stereo system or lighting system may require big amps. just curious

[Matthew Abate]

Not sure yet. Just doing research at the moment.


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[Martzedcars]

If one go's to a bigger alternator, you will need bigger wiring ...  standard is 60 amps, you don't need more..  When you do, and i speak here as an electrician, you will have a fair chance that one day you car catches fire..

If you want more reserve power, go for more led-lights, you save a lot of Amps there for that loud stereo!   and you're wiring thanks you...

[Matthew Abate]

Whoa. Yeah. I hadn't thought of that. I hadn't noticed anyone even broach that subject in any of the alternator upgrade conversations that I've read.

Something else to add o the research. Thanks.

Edited February 4, 2017 by Matthew Abate

[wheee!]

Correct me if I'm wrong, but a higher current alternator will not "push" more power to anything other than the battery. The current draw from your connected devices (lights, stereo, fans etc) is set by the device. Therefore your wiring harness is just fine. Decreasing the gauge size (smaller gauge = thicker cable) of the main charging wire couldn't hurt though. Just make sure whatever device you ADD to the car gets the proper size wire gauge and fuse and you should be fine.
Background: I am a military electronic/optronic specialist....

[hatepotholez]

If one go's to a bigger alternator, you will need bigger wiring ...  standard is 60 amps, you don't need more..  When you do, and i speak here as an electrician, you will have a fair chance that one day you car catches fire..
If you want more reserve power, go for more led-lights, you save a lot of Amps there for that loud stereo!   and you're wiring thanks you...

Agreed. I was considering going all led


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[Matthew Abate]

51 minutes ago, wheee! said:

Correct me if I'm wrong, but a higher current alternator will not "push" more power to anything other than the battery. The current draw from your connected devices (lights, stereo, fans etc) is set by the device. Therefore your wiring harness is just fine. Decreasing the gauge size (smaller gauge = thicker cable) of the main charging wire couldn't hurt though. Just make sure whatever device you ADD to the car gets the proper size wire gauge and fuse and you should be fine.
Background: I am a military electronic/optronic specialist....

Is that because the alternator would just connect directly to the battery and not the harness? I think of you go with a 2-wire solution to get the low rpm charging you are connecting to the harness.

im following you on the various items pulling from the battery, though. I think. I'm not up on the wiring in these cars yet.

[wheee!]

I believe that the internally regulated alternator "senses" the voltage drop of the battery and regulates the charging voltage to the battery, preventing overcharging. This keeps the voltage output of the alternator around 13.8v while charging and prevents the battery from draining while the vehicle is running. The field wire is designed to detect the sine wave of the charging come from the properly working alternator (alternating square wave, AC voltage). The dash light illuminates, indicating a "no charge" condition when the car is not running or if the alternator is malfunctioning. 

The alternator is never connected directly to the harness in terms of charging any electrical items other than the battery. The current is then drawn from the battery through the fuse block and throughout the harness. A larger alternator will have a greater CAPACITY to support a larger load of electronics (bigger headlights, bigger stereo, electrical fans, power accessories...) but it will not force any of the existing electronics and wiring to use any of the extra capacity of the alternator. It will only provide more power when needed versus the stock size alternator. Different size wires in the harness are used because each device draws a different amount of current, some requiring a thicker gauge of wire to prevent overheating. You can have two wires connected to the battery for example, one for the starter and one for the engine bay amp. One is super thick and one is very thin. They are both connected to the same battery but each DRAWS a different current amount to operate. Therefore the wire is matched to the draw of the device, NOT the output of the alternator or capacity of the battery.

Think of it as a larger gas tank.... does the same thing as a smaller tank, only lets you go farther! The bigger alternator just lets you consume more power when NEEDED....

[Martzedcars]

Mark, your absolutely right. But what's the use of a bigger Alternator then... and as you, i recommend a thicker cable between your alternator and battery.

The danger in a bigger alternator is that some people forget the original wires to the fusebox are standard already on the small side..  add some H4 headlights and things already are overloaded..  see the topics about "smell after 15 minutes riding in the dark".  And age have made them already vulnerable.

Are there a lot of good fuseboxes?  and, those bigger alternators have bigger wiring and are heavier, no need for extra (As you all say) Pounds..

 

[bartsscooterservice]

3 hours ago, Martzedcars said:

Mark, your absolutely right. But what's the use of a bigger Alternator then... and as you, i recommend a thicker cable between your alternator and battery.

The danger in a bigger alternator is that some people forget the original wires to the fusebox are standard already on the small side..  add some H4 headlights and things already are overloaded..  see the topics about "smell after 15 minutes riding in the dark".  And age have made them already vulnerable.

Are there a lot of good fuseboxes?  and, those bigger alternators have bigger wiring and are heavier, no need for extra (As you all say) Pounds..

 

It would be no problem if you changed the entire wiring harness in the car for a modern version. I don't know if that is there for the Datsun but it put a wiring harness from american autowire in my mustang, and that works with a modern self regulating alternator

Edit: there's no harness specific for the 240Z, but there are " universal kits " that if your handy, can make fit into the car. Like this one:

https://www.summitracing.com/int/parts/aww-500703/overview/

Edited February 5, 2017 by bartsscooterservice