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'77 620 Alternator wire colors help needed


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Thank you to ggzilla for your post last May that helped me determine that my alternator is good. I'll be checking my external voltage regulator next.

 

I need to make sure I'm connecting the wires correctly to the "F" and "N" terminals of my Hitachi alternator. My problem is that the "Tee" connector that goes to those terminals is completely gone. I have two female crimp spade terminals to connect to the alternator. Does the yellow wire go to "N" and the white/ black wire go to "F"? I see conflicting information in my Haynes repair manual. Can somebody take a look at their truck for me?

 

I've included the illustration from the Nissan factory manual that ggzilla used:

 

18733.jpg

 

Thanks,

Dan

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Thanks for responding, nukeday. yeah, that is an excellent site packed full of valuable info that's helped me alot already. I'm certain my problem is a bad voltage regulator. There should be a +12VDC output from the "F" terminal of the regulator (white/black wire) going to the alternator "F" terminal, which allows the alt. to charge the battery, but the voltage isn't there. I ground off two case cover rivets to peak inside the regulator, and found it's a solid state type. I pretty certain it's bad. I just bought one on ebay a few minutes ago.

 

Dan

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I'd like to share something to check for when troubleshooting alternator/ external voltage regulator problems. I was at a loss to understand why, on my "77 620, even with a new solid state electronic VR just installed, that I still wasn't getting the alternator to charge the battery. After describing the problem to an auto mech. friend, he reminded me that the VR needs +12V to it's "IG" terminal (white/blue stripe wire) so the VR knows to turn off the cutout to the alternator "F" terminal when the engine is running. The cutout needs to be off with engine off to prevent the battery from discharging through the alternator field winding. Anyway, with engine off and ignition switch "on", I had no 12V at the VR engine harness connector. I traced the problem back to the upper lefthand fuse in the fuseblock under the dash. The fuse was good, but one of the fuseholder clips was intermittent, which I discovered by accident with the voltmeter probe tip. If I pushed on the clip just right, I'd get the 12 V at the VR. After reconnecting the VR and starting the engine, my alternator was charging the battery again. The fuse clip is riveted through the fuse block to a copper bussbar on the rear of the block that has 12 V applied when the ignition switch is on. I guess that the rivet is just loose enough to create the intermittent condition.

 

Dan

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