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Guest Message by DevFuse

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Alternator wiring for ej swap

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#1 snofool


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Posted 25 February 2014 - 02:36 PM

The other day I changed my spark plugs, easy enough. Until I hooked up my optima battery backwards! I wasn't really paying much attention I guess. I have never done this on anything before. The key was never turned on, none of the fuseable links were burnt or affected. But the alternator fried the diodes. Puff of smoke and gross electrical smell.

So I took the alternator and got a reman from auto zone. Now when I hooked everything back up I was not charging to my knowledge. I was only getting 12.05v from the battery terminals while the car was running. Also as I run the car and use the accessories like lights, fan,heater fan, and so on, I see that the voltage meter is dropping in volts as I turn on more accessories.

Currently I do not have the yellow wire in the alternator plug harness hooked up to switched power. Does this wire need to be tied into a switched power source to activate the voltage regulator? I will try and take some pictures for more clarity.

I currently have the wiring as labeled below

90' 2.2 3wire alt plug.

White from the plug ties into BLK/White(ea harness)


Blk/White from the plug goes to charge light Red/White(ea harness)


Yellow wire was not connected.         


I have read that people have hooked this yellow wire to a switched 12v power source. To activate the voltage regulator.


I have not had this wire hooked up before and my battery after 5400mi on the swap is still @12.5v

Do you think this has anything to do with the new alt needing this switched wire? If so can I tie into the coil wire from the old harness? This is the most accessible 12v switched source to my knowledge. Thanks for any advice!

Edited by snofool, 25 February 2014 - 02:38 PM.

#2 Gloyale


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Posted 25 February 2014 - 09:17 PM

Correct hookup would be the to hook the yellow EJ wire to the 12v Ig. switch yellow wire that triggers the EJ harness on....but not needed to be that way.


Simplest would be to hook the White from plug to the main White charging wire.......That's how it is in the EJ car.  Redundant...


Then hook the Yellow EJ wire to the Blk/white EA wire.....which should be switched power same as coil + wire...


Black/White EJ wire is correct as is to the White/red EA wire.



Make sure your Fusible links are intact as well......could be as simple as a fried link.

#3 snofool


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Posted 26 February 2014 - 12:19 PM

Thanks for the reply. I was reading in here in a couple  other spots about this but it was sorta unclear. I will try this today and report my results.


All I needed was this yellow wire hooked up to a switched wire to get the proper voltage to the battery.

The old alternator was not hooked up this way but the new one must need it to control the voltage regulator.  Now I get 14.4/14.5 

Edited by snofool, 26 February 2014 - 04:22 PM.

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