Jump to content

1971 Datsun 521


Recommended Posts

  • Replies 490
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Posted Images

My truck didn’t have t connection so I went of the diagram. White/black was my L or field f im the old alternator and sence yellow wire. The yellow has to be connected to a switch source right from what Matt said


old harness was cut and just had female connectors and the new and I don’t have the plug for the la so I’m using female connector like how it was on the older l16 alternator before the swap

Edited by Zonargx
Link to comment

well one of the 521 wires the yellow or the blk /white is switched from the Key

I have to go check that out to be sure. but Im off line for awhile in a couple mins


damn that the drawing I was looking for


if its wires this way as the drawing  and you dont have a electric choke relay

then have the alternator check out

Edited by banzai510(hainz)
Link to comment

So now I’m thinking what if my battery won’t charge good like has a dead cell does the sense wire detect it’s low and try to make the alternator work this using power and then draining the battery? Sorry I’m not that experience with car in-depth electrical stuff just the basic

Link to comment

I doubt this will add any answers, but maybe some clarity.  


The continuity tester is like the ohms setting on a multimeter. It has a battery inside it that will turn the light on when the circuit is completed...in other words, has continuity.  There are higher end test lights that look like yours that do multiple types of tests....continuity being one of them. You do not have that.
Your test light lights when there is an external battery (voltage) providing the juice.  When you connect the ground cable to ground and then the tip to something providing voltage, it will light.  Be careful putting it in series because if the drain(load) is too high, it will burn out the bulb.  So, putting the test light between the neg term on the batt and the battery cable(disconnected) will show small drains(current flow), but if you were to turn your key to start, you'd probably burn the bulb out because of how much load(current) it was trying to pass.  

You multimeter's amp setting probably only handles 10mA.....which is not much. Most users kill this function trying to check current by doing the same thing that burns out the bulb in the test light....putting it across a load drawing too much current.


This may answer some questions about the alt connections... http://datsun1200.com/modules/mediawiki/index.php?title=IR_Alternator_Conversion_Wiring   It does say in there that the F wire to the alt is constantly hot, even when the car is off.


Alternators do not have permanent magnets in them like generators. They require a small amount of external voltage to "excite" the windings.  They create a field(EMF) that induces the voltage into the main windings once the the pulley is spinning. The secondary windings have to be moving for this to happen....no motion, no volts.  Once it start spinning, the main(battery) output of the alt is looped back to the N(S) to keep providing the "excite" voltage.  That's the white/yellow jumper.  It's constantly HOT because it comes directly from the battery. The diodes should stop it from back feeding or draining the battery.   The F terminal is basically the same as the B, but not made to handle as much load.....so it goes to the CHG(IGN) light or other meters/test indicators.  Your WR/WB jumper is simply to make the CHG light work.


So.....connect the batter cables......then connect the grd clamp of your light to the neg term.  Remove the S line from the alt and probe it....it should light your test light, proving it's always hot as it should be.  The big wire on the back of the alt should be hot as well. Once turning, it puts out a higher voltage than the battery and charges the battery.  With the motor running, that wire should have about 14.4 volts on it.  If not, you probably have a bad alt......make sure the S wire is hooked back up first.  


Hopefully, I'm right on all of this. It's been a really long time since I've even looked at this stuff. The 1200 page has some great info on it....default to it if I'm wrong about any of this. lol  


I should have been in the shop an hour ago.  Gotta run. Good luck!






Link to comment

So then my diodes are probably bad because they drain my battery ? It didn’t use to do this before even after the ka swap. Everything is still wired the same. If after removing the sense and light goes off that stops the drain once plugged in the diodes drain it. Are the diodes grounding out or something? Reason my test light goes on with any metal

Edited by Zonargx
Link to comment

Short answer...yes, it sounds like at least one of the diodes is shorted.  


Long answer....

Sounds like you have a multimeter. If so, go to the ohms/resistance setting.  Hopefully, it's auto ranging, but if not, a setting in the middle is a good place to start...200? 2000? If it's auto ranging, ignore the comments about changing the range.  If it's not, you'll need to keep switching the range from lowest(to check a sort) to highest(to check an open). Touch the leads together. It should show a short....zero ohms or really close....that proves that the meter is working. Disconnect the wires(all) from the alt.  Put the neg lead to the case of the alt and touch the pos lead to the E on the alt.....you should get zero(or near zero) ohms. This proves you have a good ground(continuity between the case and the E terminal.  Now touch the pos lead to the other terminals on the alt.  Set the range to the largest selection and it should still show an open(really high ohms....meg ohms).  If the alt is bad, you'll probably see a very low reading. To see the lowest ohm reading, turn the range down on the meter.  Reverse the leads.....pos on the E or case and neg on each of the terminals.  The B post(main alt output) should be an open with the leads on this way and then a low resistance when the leads are switched to the other way.  There's lots of videos on YT about how to test the alt with a meter.....check some of those out.  I'm so rusty at this stuff, I may just be muddying the waters. lol  This is a good vid, but way more involved than what you need. At the 12 min mark, he does the test I just described. Check the vid for his AC test....if a diode is bad, I think the AC volts will be high.



....more good info... https://www.yesterdaystractors.com/cgi-bin/viewit.cgi?bd=farmall&th=1082507


....and if you want to know everything about how the alt works...... chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/viewer.html?pdfurl=http%3A%2F%2Fwww.metroplexalternator.com%2Fuploads%2F1%2F5%2F2%2F8%2F15280940%2Fcharging_system_theory.pdf&clen=1653762&chunk=true

Edited by mklotz70
Link to comment

Checked the alternator it was good. I just hook the sense to an ignition on switch source and hasn’t drain the battery so far so I’ll just leave it like that for now thanks for the help everyone thanks thisisMatt for the ignition source tip

Edited by Zonargx
  • Like 1
Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...

Important Information

By using this site, you agree to our Terms of Use.