Alternate Alternator Upgrade - Nissan/Infiniti

[Bob Weir]

Cluster / Alt Light 2 Blue wires
a] Park Lamp Relay
b] Engine Run Relay -> Voltage Regulator

Hoes your Nissan Alternator handle Voltage Regulator?

[DPDISXR4Ti]

Cluster / Alt Light 2 Blue wires
a] Park Lamp Relay
b] Engine Run Relay -> Voltage Regulator

Hoes your Nissan Alternator handle Voltage Regulator?

The White w/ red Lamp wire from the Nissan alternator quick-connector is butt-spliced into the blue wire that goes to the cluster. It's pretty much a function-for-function swap with the original Bosch alternator. I did note that the blue wire wasn't in such great shape, even where I cut it back to about 2" from the original connector. Instead of nice clean copper wire being exposed, I got tarnished copper.

Like the original Bosch alternator, the Nissan has it's voltage regulator built in. Admittedly the Bosch VR is more readily serviceable from the outside of the case, but maybe that's because it requires more frequent replacement.

[DPDISXR4Ti]

The only odd thing is that the battery light on the instrument cluster stays dimly lit now. Hmmmm....

Lots of info out there on dimly lit battery lights....

"The battery light is driven by the regulator inside the alternator. If the regulator detects a problem, it will ground an output, causing the battery light to illuminate. If the light is on but dim, then there is a weak ground somewhere. It could be the regulator, the wiring between the regulator and the instrument panel, or the instrument panel itself.

First, turn the car on (but don't start it) and verify that the battery light is on full brightness. Then, turn the car off and unplug the 2-pin connector (in the case of the Nissan alt) at the alternator. With that connector disconnected, turn the car on, but again don't start it. The battery light should be off. If it's off, then there's most likely a a problem with the regulator or the alternator and the alternator should be replaced. If it's on dim, then there's a problem either in the wiring or in the instrument panel."
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A quick alternator diode test...
https://youtu.be/xgikeXt91vM
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[DPDISXR4Ti]

A quick alternator diode test...
https://youtu.be/xgikeXt91vM

And this ^^^ provided my answer. My alternator failed the diode test. I guess this is why I picked up a second backup alternator before I even installed the first one! If only I had tested these both up-front and installed the good one.

Now I get to see how easily I can R&R the alternator with everything installed.

[Ed Lijewski]

Simply cannot understand guys with our resources not buying a remanned alternator to install once and forget about for years and years instead of used JY units.

YMMV

[DPDISXR4Ti]

I spoke too soon. Dummy me, I didn't realize that you need to have the big B+ wire removed when you do the alternator test with it still mounted to the engine! This video details that fact... https://youtu.be/dhf6IdBbE3Y

Any way, with the alternator removed, it bench-tested fine. I think. It measured ~350 microvolts. The video above indicates that it should be between 500 and 800. In fact, the other alternator measures around 600 microvolts, so that's the one which will be going in now.

[DPDISXR4Ti]

My second 110A Nissan alternator is now installed in the car and it functions as it should, just as the first one did. BUT, I still have the dimly lit battery light in the instrument cluster. I guess I need to dig deeper on that issue. Funny enough though, about half the hits I get for "battery light dimly lit" talk about how they left it alone and all was fine. But I can't do that.

Here's an older thread on Bimmerforums where a guy (Tom D) provides some good advise on debugging a similar issue. Conveniently, BMW used the same blue color wire for the "Excite" circuit that goes back to the cluster, so I don't even have to color-translate that advise.

https://www.bimmerforums.com/forum/show ... ld-be-good

Another little test....
I had same problem years ago and added a additional ground strap between alternator case and engine block. You can confirm the need for the second ground with a volt meter by placing the leads between the alternator case and block. With the engine running, .5 or more volts difference showing between the two will give you the faint glow of the battery light. You could do the same thing checking for resistance between the two with the engine off and the volt meter set to read resistance.

And some insight on how the circuit works... (Note, D+ is the Excite circuit - the blue wire, B+ is the big 12V+ wire that goes to the battery)
"There is one wire coming from the dash alt light over to the alt. With the alt not running, the D+ terminal is close to ground potential and the light turns on. When the alt is running, the D+ terminal has the same voltage at the B+ terminal and the light turns off. If the light is slightly on, the alt D+ terminal is at a voltage lower then the B+."

[DPDISXR4Ti]

A couple little discoveries as I'm (literally) unravelling the harness and studying the schematic.

1) On the big factory B+ wire (circuit 51) that goes to the alternator, underneath the decaying tape, midway between the battery and the alternator you'll find splice S102 that has this small gauge red wire(circuit 30-9) that powers the hazard flasher. Seems like a crazy idea that I won't be replicating with the new larger cable to the alternator. I'll just lengthen the wire a bit and run it to my new Volvo fused power distribution box.

2) The D+ blue "Excite" wire (circuit 61) takes a longer trip than I expected. It goes through Connector C1936, then to pin 86 of the Engine Run Relay, and only then does it proceed to the "idiot light" in the instrument cluster. Lots of places for a voltage drop, which is pretty much what I'm chasing at this point.
Update... Despite having the dash out, I couldn't find C1936 so I moved on to pin 86 of the Engine Run Relay and measured .5 Ohms between there and the alternator end of the circuit. Moving upstream and measuring resistance to the + side of the battery light bulb contact on the back of the instrument cluster I get .7 Ohms. Given that I had a few wires with alligator clips involved to make this test, I think I've got a good circuit here and circuit 61 is checking out okay.

I can't really figure out why the new alternator has caused this issue to appear. What does it do different with respect to the D+ circuit? If it was easier to do than it is, I'd swap the original Bosch alternator back in, just to make sure the issue isn't now there regardless of the alternator. I suspect it would in fact "go away" with the old alternator.

[Ed Lijewski]

I'd only observe that it's not a "new alternator"...it would have been prudent to have it tested for free at an auto parts store before installing it.

I had three separate Scorp alternators tested--original in car unit and two JY units--tested, neither unit passed. Then I went remanned alternator and haven't looked back.

YMMV

[brokencase]

OK, Let me first state that my alternator is different. I have the 130 amp unit and I believe Brad's is the 110 amp unit.

That being said, I don't believe there is any difference, but there could be.

As I understand it, the lamp wire works as follows...

The high side of the lamp is connected to +12v. The lamps lights when you first turn the key to ACC because the alternator is not yet spinning and the other side of the lamps sees ground.

Current through the lamp (maybe a 100 milliamps or so) provides a seed current through the field windings of the alternator. The alternator has no permanent magnets, the field coils fill this role.

As the alternator begins spinning it becomes able to self generate the field voltage and the lamp wire rises to 12v.

You then have 12 volts on both sides of the lamp and hence it goes out.

The old Bosch alternator definitely worked this way. I think the Hitachi works this way also but it is also possible that the more modern regulation circuitry mimics this behavior and it may be able to manage the seed current internally and the lamp is just an indicator. This allows them to turn on the lamp for other reasons.

I really think you should have wired it as I indicated...i.e., with the separate sense wire.

Also make sure you have not replaced the alternator lamp in the dash with an LED. That won't work.

It could also be the case that you have the wires confused.

[DPDISXR4Ti]

Thanks for the input Dean. After testing the integrity of the blue wire back to the cluster, I decided l need to follow your lead and wire things up exactly as you have, including a new sense wire back to the battery. I almost finished before running out of steam a couple hours ago. Included in that is an entirely new main wire to the alternator - I think it's 4 gauge, about double the thickness of the original.

It's also occurred to me that perhaps the quick-connector wires are opposite for the Mitsubishi alternator vs. the Hitachi you used, even though the connectors are the same fitment. It seems very unlikely, but I'm keeping all options on the table.

No LED bulbs in my cluster, so that wouldn't be the issue.

[DPDISXR4Ti]

Here's a link to a schematic for the 2006 Nissan 350Z charging circuit. It shows the White/Red wire going to the instrument cluster and Light Green/Black wire going to Hot At All Times 12V+ fused by a 10A. So I've confirmed that the wiring is the same between the 2-wire Hitachi and Mitsubishi alternators used on the Nissans.

https://portal-diagnostov.com/cs/2020/0 ... -diagrams/

[DPDISXR4Ti]

Ran the sense wire directly back to the battery and no change - still get the dim battery light once started.

Checked voltage across the battery terminals while running and I get 14.45V, so clearly the alternator is doing it's job. Measuring output at the alternator stud I get 14.47V, so very little difference.

At the moment I'm out of things to try.

[DPDISXR4Ti]

The old Bosch alternator definitely worked this way. I think the Hitachi works this way also but it is also possible that the more modern regulation circuitry mimics this behavior and it may be able to manage the seed current internally and the lamp is just an indicator. This allows them to turn on the lamp for other reasons.

I tested this function by removing the battery light bulb in the cluster and then starting the engine. I had 11.8V at the battery, so clearly it was not charging with no bulb in place. It sure seems like it operates the same as the Bosch.

[brokencase]

The old Bosch alternator definitely worked this way. I think the Hitachi works this way also but it is also possible that the more modern regulation circuitry mimics this behavior and it may be able to manage the seed current internally and the lamp is just an indicator. This allows them to turn on the lamp for other reasons.

I tested this function by removing the battery light bulb in the cluster and then starting the engine. I had 11.8V at the battery, so clearly it was not charging with no bulb in place. It sure seems like it operates the same as the Bosch.

Good to know.

If your battery is sitting at 11.8 volts statically then it is in a low state of charge. Perhaps this is why the light is dim?

You now know the alternator works. Now charge the battery up with an external charger and then start the car to see if the dim light goes away.