Help with factory alternator harness on '72 240Z

[RJK]

Hi all, I installed an MSD ignition in my '72 Z, and now the alternator is way under-spec-ed. Battery dead after 10 minutes of driving. I installed a new 70amp alternator from z car depot, and have one question about the factory harness. there's a 2 pin harness that runs to the old alternator location. the new has a tab labeled "ignition key on". I believe I'll need to manually wire this lead to one of the two pins of the car's harness. i can't tell if its the yellow wire, or the white/black wire. Any help would be appreciated. I found this data point on the 280z:

 

• F&N (T connector)  
  N (Yellow) (on the early alt becomes the Sense signal on the newer alternator (the alternator "senses" the voltage on this wire and attempts to maintain it at 14.45V. 
  F (white with black stripe) is the Field signal on the early alt that becomes the L lamp signal on the newer alternator."

[SteveJ]

1 hour ago, RJK said:

Hi all, I installed an MSD ignition in my '72 Z, and now the alternator is way under-spec-ed. Battery dead after 10 minutes of driving. 

Um, that would not be caused by an MSD ignition. That would be caused by some combination of old battery, bad alternator, and bad voltage regulator.

Post pictures of what you're talking about with regard to the new alternator.

[Zed Head]

4 hours ago, RJK said:

 "ignition key on". I believe I'll need to manually wire this lead to one of the two pins of the car's harness. i can't tell if its the yellow wire, or the white/black wire. Any help would be appreciated. I found this data point on the 280z:

 

• F&N (T connector)  
  N (Yellow) (on the early alt becomes the Sense signal on the newer alternator (the alternator "senses" the voltage on this wire and attempts to maintain it at 14.45V. 
  F (white with black stripe) is the Field signal on the early alt that becomes the L lamp signal on the newer alternator."

It would be the F wire.  Don't forget the diode.  And don't forget to disconnect the old external regulator.  The best way to "connect" that wire is to jumper it at the VR plug.

https://www.atlanticz.ca/zclub/techtips/alternatorswap/index.html

[SteveJ]

1 hour ago, Zed Head said:

It would be the F wire.  Don't forget the diode.  And don't forget to disconnect the old external regulator.  The best way to "connect" that wire is to jumper it at the VR plug.

https://www.atlanticz.ca/zclub/techtips/alternatorswap/index.html

This is why I asked @RJK to post photos. What @Zed Headposted is 100% correct for a 280ZX alternator. HOWEVER, I believe @RJK could conflating the 280ZX alternator with another 70 Amp alternator sold by ZCarDepot. 

This is the other alternator that is explicitly listed at ZCarDepot.

 

[Zed Head]

I don't think that any of the 70 amp alternators are externally regulated.  The only external is a 60.

https://zcardepot.com/search?q=alternator&type=product

https://zcardepot.com/products/alternator-reman-240z-260z-280z-510-70-77?_pos=12&_sid=673ff5c1a&_ss=r

The guy at ZCarDepot is being disingenuous in his ad copy (surprise).  He says that it is a "direct replacement".  But it's not.  Caveat emptor.  Or, also possible, the guy at ZCarDepot is ignorant of how the alternators work. 

https://zcardepot.com/products/alternator-high-amp-80-240z-260z-280z?_pos=1&_sid=673ff5c1a&_ss=r&variant=19280584015985

New direct replacement high amp alternator for Datsun 240Z, 260Z, 280Z and 280ZX, 1970-83. This alternator is rated at 70 amps and bolts up in the same location as the original. Internally regulated. Datsun Z cars 1970-77 have an external regulator so the external regulator will no longer be used. Alternator uses standard flat male/female connectors or you can purchase the optional connector.

*Optional connector plugs right into alternator. Yellow wire connects to switched 12V and green wire connects to the positive post on the alternator

 

Edited September 24, 2021 by Zed Head

[RJK]

Ok, so this is the alternator I'm going in with:

 

https://zcardepot.com/collections/charging-starting/products/alternator-high-amp-80-240z-260z-280z?variant=19280584015985

harness is kinda hard to see, but one wire is yellow, one is white/black.

 

[SteveJ]

Have you jumpered out the external VR?

For the switched wired, you may want to get a 6.3mm 2 pin connector from http://vintageconnections.com/Products/Connectors

On the wiring harness T connector, the vertical part of the T is the switched wire. As @Zed Head said, you will probably need a diode on the switched wire, otherwise, you may backfeed the ignition circuit. The arrow (line) on the diode points toward the alternator. The diode can go between the green wire and the connector, or it can be integrated into the jumper for remove the external VR from the circuit.

[Zed Head]

SteveJ, I think that he has been bamboozled by the "direct replacement" words on the ZCD site.

 

The instructions on the ZCD site are incomplete/wrong.  And you could have bought a 60 amp 1978 280Z alternator at your local parts store for about $65.  You do get an extra 10 amps though.

Not worth trying to get a refund.  Read that atlanticz link.

[SteveJ]

Just now, Zed Head said:

SteveJ, I think that he has been bamboozled by the "direct replacement" words on the ZCD site.

 

The instructions on the ZCD site are incomplete/wrong.  And you could have bought a 60 amp 1978 280Z alternator at your local parts store for about $65.  You do get an extra 10 amps though.

Not worth trying to get a refund.  Read that atlanticz link.

It's what I suspected. I don't think the people at ZCarDepot are not being intentionally deceptive. They understate the changed necessary to integrate the GM alternator into the Z wiring. It would be nice if they just mounted the proper T connector to the alternator AND advise buyers about the need to jumper out the VR for the 70-77.

[Zed Head]

I think it's just one guy.  He used to be a Z guy.  He should know better.  Pretty common, you can find the stories of the guy who started selling a few parts, got bigger, and things started to go bad.

I just call things like I see them.  The benefit of doubt just facilitates more problems, I think.  Call 'em out early so they can fix them before they get a permanent bad reputation.

The instructions on the "high amp" alternator page are misleading.  They lead people to buy a product, because it's a "direct replacement" that won't work if they follow the instructions that are used to make the sale.  Once the part is connected wrongly, it becomes a "used" electrical part which gives the vendor the excuse not to refund the money.  It's very close to being intentional.  That's how it looks to me.

[Zed Head]

And, if you have "Z Car" in your name you are implying expertise in a specialty area.  If you're not sure it works correctly you shouldn't put it on your web site.  Right?  Just saying, he's not just another O'Reilly Auto Parts.

 

[RJK]

1 hour ago, SteveJ said:

Have you jumpered out the external VR?

For the switched wired, you may want to get a 6.3mm 2 pin connector from http://vintageconnections.com/Products/Connectors

On the wiring harness T connector, the vertical part of the T is the switched wire. As @Zed Head said, you will probably need a diode on the switched wire, otherwise, you may backfeed the ignition circuit. The arrow (line) on the diode points toward the alternator. The diode can go between the green wire and the connector, or it can be integrated into the jumper for remove the external VR from the circuit.

I have not jumpered out the VR. I will grab that 2 pin connector What spec diode do I need? As much as I'd like to think I'm a competent guy, I'd love to have a comprehensive list of everything I need to do to wire the new alternator correctly. As I was under the impression that the alternator was a drop-in replacement, and was internally regulated, the ZCarDepot site let me to believe I could drop this in. I briefly tested the battery connections after wiring up the alternator, and smoked a bit of insulation off of a starter wire(looks like I did indeed briefly backfeed the ignition circuit). I really wanna do this safely and correct. There is a good amount of data of alternator swapping across years/models for Z cars out there, and a lot of it varies. I really appreciate you guys stepping in and helping me out, especially since the data on the ZCarDepot site seems to be not only lacking, but potentially dangerous. Thanks.