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

[Matthew Abate]

if the main wire feeding your fuseblock is too small, then yes. it doesnt matter how big the alternator is, if the wire is too small to carry the total load, you will have problems. you might think of adding a second fuse block that feeds the add-on goodies. also keep in mind that clean, tight, corrosion-free connections and grounds will help.

Man, I almost feel like building a harness from scratch is the way to go regardless of whether or not mine is any good, which is something I wasn't going to look into until the car is getting painted.

[wheee!]

11 minutes ago, Matthew Abate said:

 

 

Man, I almost feel like building a harness from scratch is the way to go regardless of whether or not mine is any good, which is something I wasn't going to look into until the car is getting painted.

 

That would be overkill and lead to potentially more issues if the harness is not built correctly. I would replace the lines that are damaged, or lines that are undersized. Lines to the battery from the  alternator, line from the battery to the starter (if needed), and line to the main fuse block (if you plan on adding circuits). Otherwise, adding a fuse block like the one I pictured above will provide a fused power takeoff for any new accessories.

[Matthew Abate]

I'll take it slowly and reach out as I progress. Excellent discussion, guys.


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[Captain Obvious]

15 hours ago, Matthew Abate said:

headlight upgrade, fog lights, two USB plugs, the engine, the dash lights, the heater fan, seat heaters, and LED marker and tail lights, and the interior light *might* be too much for the ZX alternator upgrade

Actually, to the contrary:

The headlight upgrade won't do anything to change the overall total requirement. The original system was already designed to provide power to headlights, so it doesn't change your total draw from stock. And in addition to that, if you do the upgrade with the purchased plug in harness, it will reduce the load on the fusebox because the high current part of that system will come directly from the battery through new wiring that includes a new fuse for the headlight current.

I haven't actually researched the power draw of devices you plug into them, but USB plug draw might be ignorable. Any idea what power you will pull through those?

You already have a heater fan and the original system was designed with that in mind. So the same thing applies here as to the headlights. Doesn't change your total draw from stock.

Changing to LED lights anywhere will be a system current reduction, not increase, so no alternator upgrades needed for that.

Bottom line with your list so far? You're adding seat heaters and need to account for that.

And if your LED lights reduce the system draw by the same amount that the seat heaters increase it, you're at a net zero change and don't need any alternator upgrade at all. You have to pay attention to the wiring to the seat heaters, but so far, you might not be needing anything more than stock.

[Matthew Abate]

Nice. The USBs will be for phone charging and maybe a Sat Nav. The one thing I forgot was some kind of power supply for a Bluetooth speaker system, which will be identified after the car is nearly done (think Bose Soundlink mini or similar). I'm planning to leave the stock stereo system and replace it with the JDM box that fits in the center of the dash.

I'm probably digging into this before I'm ready, but it's on my mind because the alternators I have are not in great shape and the engine rebuild is progressing.


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[Zed Head]

A point of reference that could help people mentally get hold of the capacity, or supply, versus load, or draw, difference - a typical battery has 500 - 600 amps available at an instant.  CCA.  That's why when you connect a wire wrong, and create a low resistance path to ground, or high draw, you can vaporize a wire in a flash.  In other words, we all have a 500+ amp power source sitting in the engine bay right now, that dwarfs any alternator you could find..

So it's not the supply side that matters, it's the draw side,  Any discussion about wiring harness weakness should really never even mention the alternator.  The battery power will do the damage. 

[Patcon]

ZH

That was part of my point earlier. How long will 500 CCA's run what ever you exceed your 60 amp alternator for? A good while I would think if it's healthy...

Also CO made my point also about being out in the rain. Most of these cars when reworked to this level tend to avoid rain for the most part...

[siteunseen]

1 minute ago, Patcon said:

Also CO made my point also about being out in the rain. Most of these cars when reworked to this level tend to avoid rain for the most part...

I can't remember ever having my wipers on but mine isn't a DD.  I'll check the functionality next wash just in case. 

 

[Zed Head]

11 minutes ago, Patcon said:

ZH

That was part of my point earlier. How long will 500 CCA's run what ever you exceed your 60 amp alternator for? A good while I would think if it's healthy...

Also CO made my point also about being out in the rain. Most of these cars when reworked to this level tend to avoid rain for the most part...

I wanted to separate the "upgrade your wiring harness if you upgrade your alternator" issue out completely from the discussion.  It comes up a lot and it kind of jumps in to people's thought process, and kind of makes sense.  Basically confusing voltage with current/amps.  The alternator is irrelevant to burning wires unless it shorts out.  Even then it's the battery doing the damage.

Many people probably add all of the extra loads at the same time they add a higher capacity alternator.  Then when wires melt or fuses blow they blame the alternator instead of the loads.

There's the whole other side discussion also about alternator idle speed supply versus maximum possible.  Another important detail that gets overlooked.  Kind of like peak horsepower versus usable horsepower, or power under the curve.  Details.  I bumped my idle speed up about 100 RPM and made things a lot better.  

[ksechler]

6 hours ago, wheee! said:

That would be overkill and lead to potentially more issues if the harness is not built correctly. I would replace the lines that are damaged, or lines that are undersized. Lines to the battery from the  alternator, line from the battery to the starter (if needed), and line to the main fuse block (if you plan on adding circuits). Otherwise, adding a fuse block like the one I pictured above will provide a fused power takeoff for any new accessories.

Ditto, but something to consider would be adding another fuse box with a sub-harness for your accessories.  You could use a relay and pull things in off the ignition.  I took that route with my fans, vacuum pump, ignition and fuel pump. If you look it the picture below the fuse box is above the inspection lamp.  The relays are all about dead center in the picture.  

 

[wheee!]

We're starting to repeat ourselves

[Dreamzz]

Going back to beginning of this thread.....
Has anyone installed and used the 125 amp bolt in alternator available from The Datsun Store that might be able to provide some insight .
I'm thinking of getting it for low idle amps. Can't really swap to smaller pulley on my Zx 60 amp alternator I'm running now due to direct fire triggered ignition. Alternator Pulley belt won't clear trigger sensor.


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