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521 Saturn alternator upgrade question


Datsunking

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Use L for the light.

 

Don't bother with F. It can be used in fuel injected cars to better control idle speed when there is a large load on the alternator. In your case, you'll actually see RPM's drop as you turn the lights on or off. This is normal, since the turning of the alternator is being loaded up by the bridge rectifier.

 

S is the "sense" wire and needs to be hooked up to a primary voltage source. Since the B or BAT post on the alternator is the main output, and connected either directly to battery + or the starter solenoid post, you can just jumper the S wire directly to the B output post, since it will always be seeing voltage from the battery. The S wire will detect a voltage drop either at start up, or when blipping the throttle right after start up. This will kick the alternator on. Technically, the sense wire is hooked up downstream somewhere (like the ignition switch, or on the other side of the fuse block) to get a better idea of voltage drop in the entire system, but for simplicity sake, and since these trucks don't have many electronics, it's safe to just jumper to the B post.

 

You'll also need to add either a large fuse or a fusible link between the B output post of the alternator and the battery.

 

593274d1501251471-wiring-cs130-style-alt

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I had the two wires for the exciter and the charge light reversed for several years. Then I added a volt gauge but as it was new I didn't look at it much, just forgot. When I did on one of my long Canby trips it was not charging which freaked me out. Several stops later for gas and when I restarted it... it began charging and did so until I next shut it off for gas. I borrowed an alternator from HRH and kept going with it sometimes charging often not. 

 

So what was happening was the battery would discharge when not charging but once it got somewhere below 11 volts, (but before without the gauge I didn't know this) the next time I would start it boom! it would kick in and charge. One time in eastern Washington I watched the voltage drop to 11 and I honked my horn just to see if it was weak and the lights flickered and up went the voltage to 14+. When I got home I swapped the wires and it's been good ever since. In my case having them reversed was no cause for worry, no harm done after 3-4 years wired wrong. I should have guessed this and later figured it out because the charge light never came on when the ignition was turned to on. 

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  • 6 months later...

Cheers to reviving a dead thread. I’ve been diligently scouring the forum regarding the Saturn swap and I’ve seen a mixed bag of modifications that need to be done.

 

Putting this in a 74’ 620 with an L20 swap. I’m good on the wiring, but what structural changes need to occur? Do I need to change a hose inlet? Bracket changes?

 

Suggestions are always welcome.

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