Help with factory alternator harness on '72 240Z

[SteveJ]

For the diode, you can find a description here: http://www.zhome.com/ZCMnL/tech/280Alt.html

For the jumpers at the VR connection, you can get the 6.3 mm 6-pin non-latching connector from Vintage Connections. You can use that connector for the diode. 

1. Unplug your VR.
2. Set a multimeter on continuity.
3. Look for the black/white wires from the engine bay harness going to the connector. Test each for continuity with the vertical pin on the T connector at the alternator.
4. The diode would point to the T connector.

You can also check with Motorsport Auto to see if they have this in stock: https://www.thezstore.com/page/TZS/PROD/classic12h04/12-4067

It already has the diode.

[w3wilkes]

Here's a pretty good blow by blow of going to an internally regulated alternator if the zstore adapter is still not in stock.

240z alternator upgrade (instructions w/ pictures) - Electrical - The Classic Zcar Club (classiczcars.com) 

[Zed Head]

1 hour ago, w3wilkes said:

Here's a pretty good blow by blow of going to an internally regulated alternator if the zstore adapter is still not in stock.

240z alternator upgrade (instructions w/ pictures) - Electrical - The Classic Zcar Club (classiczcars.com) 

That's about as good as it gets for the OP.  1972 specific.

[RJK]

This is fabulous! thanks much folks. This makes the 6 pin harness wiring very straight forward.

 

I'd still like to confirm a few things, just so I'm going back in as close to 100% sure as I can:

 

1- the 2 pin T connector that is at the alternator; how is that wired to the alternator itself? It looks like the only wire one of those tabs could connect to is the "ignition key on" tab of the alternator?

 

2-The language on the ZCarDepot site for the connector instructions is not clear at all. It refers to a yellow wire and a green wire. The actual connector they sent has a green wire and a red wire(green is the "ignition key on" tab, red is "12V post" tab, which is opposite of what they designate on the site). I currently have the red wire of the adapter, which connects to the pin labeled "12V post", tied off to the 12V post, as seen in the pictures.

 

3-this feels obvious, but I want a 2nd set of eyes on my work. The new alternator did NOT come with a bolt to tie off what I have to assume is the ground tab of the car's wiring. There is a threaded female hole in the location I'd expect it to be. The car's wiring has 2 eyelet tabs, one big and one small. I have the big eyelet tab tied to the 12V post of the alternator, and the small tab tied to this hole, with the proper metric screw seated in it. Again, seems obvious, but no stupid questions, right?

 

My only other X factor is whether I cooked off any insulation on any other wires when I briefly connected the battery to test the wiring.  I know I cooked off about an inch of one of the starter wires; I may just trace it, terminate it, and solder up a new wire for it. I know it travels thru the bundle that lives along the frame rail.

 

Thanks again for the help, folks!

[SteveJ]

1. If I understand your question, I answered it in post #7.
2. I did some digging. The alternator in your photos is probably this one: https://www.obbstartersandalternators.com/13778n-lr170-757b-lr170-757br-lr170-765-lr170-766-p-894.html. I saw the 13778N sticker in your photos. I looked up alternator wiring for the Frontier and found this: https://www.ebay.com/itm/302008182071. Picture below. That has the color wires described on the ZCarDepot site.
3. From looking at some other images online, I would think that the Earth terminal is where I have the arrow drawn in the picture below.

Can you post photos of the wire damage? Also before testing, verify which wire in the two wire connector goes where. 

If you can't see any markings on the alternator itself, you may have to resort to purchasing a Haynes manual for the Frontier to get the wiring info: https://www.amazon.com/Nissan-Frontier-Pickup-Pathfinder-Manuals/dp/1563926105/ref=sr_1_3?dchild=1&keywords=nissan+frontier+haynes&qid=1632625664&sr=8-3

[RJK]

Thanks SteveJ! really appreciate your help.

 

1-so, to clarify, on the 6 pin harness, if I integrate the diode into that connector(either via the adapter thezstore sells, or roll my own), then I would connect the tab of the alternator labeled "ignition key on" to what you referred to as the "switched wire" in the T connector with no diode in line there, correct?

 

2-the image you sent matches the image of the harness that was on the ZCarDepot site, but not the actual harness. the actual harness they sent has a green and red wire-the red wire is where the diagram shows a green wire, and the green wire is where the diagram shows a yellow wire. this would actually make more sense, as the red wire would be 12V post.

 

3-that is where I have the earth eyelet wiring from the car

 

I'll post images of the wire i burned some insulation off when I get some better light in there. thanks!

[SteveJ]

1. Correct.
2. Color is relative. Position is everything. The picture I included does not show where the green and yellow wires land on the back of the connector. I was trying to show the origin of the description from ZCD. You need to verify which wire is which on the alternator you have. In your photos, it looks like the red wire is jumpered over to the B wire. I cannot tell you with any certainty that your wiring for that is correct as I have not physically examined the alternator, nor have I been able to track down a wiring diagram. Hence my suggestion for you to buy the Haynes manual to try to track it down. Are either pin marked with an L?

[RJK]

Thanks again for all the help, guys-really appreciate it. 

 

Attached are pictures of the alternator, as well as my fried starter wire. It appears as though I could just use heatshrink, and re-insulate the wire, but I'm also happy to roll my own from scratch(I have a lot of experience soldering via building synthesizers). The portion of wire to the right of the harness appears ok, visually. It travels through wrapping along the frame rail. I can test it on a DVM and see what it connects to; if there is unseen burned insulation that could be dangerous, I could always re-run that wire section in the interest of safety.

 

On the alternator, I don't see any designations of the output tabs themselves. The +V is notated "B", ground tab is not, but it's obviously contiguous metal with chassis, so I think it's a safe assumption.

 

Does anyone know the value of the diode in question for the 6 pin harness? I've got a ton of diodes here, and could easily roll my own with female crimp connectors, but wanna go in with the right value. Thanks!!

[SteveJ]

That is NOT a starter wire. That is a fusible link. Don't know what a fusible link is? Click here: https://media.digikey.com/pdf/Data Sheets/Littelfuse PDFs/Fusible_Link_FAQ.pdf

Replace it. It is done. You can get a replacement from Banzai Motorworks (http://www.zzxdatsun.com/catWiring.php WH-03 @zspert) or  Motorsport Auto (https://www.thezstore.com/page/TZS/PROD/12-4332).

Ironically, the wire should have burned up leaving the insulation intact. In the meantime, disconnect the battery so you don't short out the link.

As for the alternator, since it does not have any identifying marks for the L and S wires, I will expand upon my previous suggestions (You need to do at least one.):

1. Buy the Haynes manual for the Frontier (98-04). The electrical section may have the information on what you need. You can get a used copy off Amazon for about $14. How much is your car worth to you?
2. Go to forums on the Nissan Frontier and see if someone with electrical knowledge can answer your question about which is L and which is S.
3. Use a multimeter on the resistance setting. If it has multiple resistance settings, you may have to repeat the steps below on 1M ohm and 1K ohm settings.
   1. Touch the common probe to the red wire. Touch the other probe to the B terminal. Record the reading.
   2. Touch the common probe to the B terminal. Touch the other probe to the red wire. Record the reading.
   3. Touch the common probe to the green wire. Touch the other probe to the B terminal. Record the reading.
   4. Touch the common probe to the B terminal. Touch the other probe to the green wire. Record the reading.
   5. Repeat steps 1-4 replacing the B terminal with the E terminal (grounding point).
   6. Report your readings from each step. If it's like the ZX alternator, I should be able to tell which is L and which is S. I'll explain what I'm looking for when I see the results.

 

Edited September 27, 2021 by SteveJ

[Zed Head]

Might be that somebody left the fusible link out and that is "real" wire.  Anyway, I'd be wondering why it burned up.  Maybe somebody connected the (A) B+ wire to the E terminal at the alternator.

ZCD actually identified the wires on his web site.  Not with proper terminology but still figurable.

[RJK]

Zed Head-yes, that diagram does show the wiring. I currently have the  "12V post" wire tied off to the B terminal of the alternator. the wiring diagram from ZCD on the harness itself is already kinda iffy, so in the interest of being thorough, i was trying to verify 100% this wiring. Thanks for that!

[SteveJ]

2 hours ago, Zed Head said:

Might be that somebody left the fusible link out and that is "real" wire.  Anyway, I'd be wondering why it burned up.  Maybe somebody connected the (A) B+ wire to the E terminal at the alternator.

ZCD actually identified the wires on his web site.  Not with proper terminology but still figurable.

Should we trust ZCD?  

There are a lot of variables we don't know about that could have contributed to the failure the insulation of the fusible link. For instance, I believe I saw paint around the connector. Paint, corrosion, etc, would adversely affect current flow, building heat. We don't know the condition of the battery. If it wasn't fully charged, the alternator would be pushing more current across the link.