Alternate Alternator Upgrade - Nissan/Infiniti

[DPDISXR4Ti]

Good to know.

I wonder if your Hitachi works the same? I wouldn't mind the dim light so much if I knew the alternator would continue to charge if the bulb burned out. As it is I'm contemplating just getting one of the Titan alternators.

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.

No, no, no. The 11.8V was with the test with the engine running and the battery indicator light removed. The battery holds a good static charge around 12.7V.

[DPDISXR4Ti]

Pulled this off a Corvette forum. Even though I've checked and double-checked the wiring, could there be something "backwards" about the way this alternator functions? Could I potentially hurt anything if I wire things the other way, if only as a test? Just looking, grasping for any possible answer....

A DIM alt/gen light is frequently caused by reversing the leads going into the regulator.....nothing to do with main stud output wiring....

EXCEPT when viewing from the rear of the alt....the MOST CLOCKWISE wire will allways have system voltage on it.....even when key is off, car parked.....

when key is in the run position , AND THE ENGINE IS RUNNING is the ONLY time the second wire will have voltage on it, what happens is the regulator pulls that wire to ground to light the bulb.....

what can happen is if the wires are reversed is when engine is running, the bulb acts to activate the reg as if it was the system wire....fed NOW through the ignition ON position of the sw.....light glows dim....

this is a frequent wiring error when replacing the connector, a famous item, and the color codes and wiring age sure as hell don't make it any easier.....

And this off an old Beetle forum....
measure the voltage to a good ground on each side of the lamp. Just curious what it would be? In an ideal world, it would be 14 volts on the ring and maybe a little bit more on the tip of the bulb. If it has, say 15volts on the 61wire - the tip of the bulb - and say 10 volts or something somewhat less on the ring the 12-volt side then you probably have a bad connection on the battery cables or something.

[DPDISXR4Ti]

And this off an old Beetle forum....
measure the voltage to a good ground on each side of the lamp. Just curious what it would be? In an ideal world, it would be 14 volts on the ring and maybe a little bit more on the tip of the bulb. If it has, say 15volts on the 61wire - the tip of the bulb - and say 10 volts or something somewhat less on the ring the 12-volt side then you probably have a bad connection on the battery cables or something.

Just did this ^^^ test and it's telling me something, I'm just not sure what.
With key in on position I get 12V on one side of the bulb and .87V on the other. Bulb is on bright.
With engine running I get 13.9V on one side and 8.8V on the other. Bulb is dim.

[Ed Lijewski]

Dean is the Pro on this but per his description recently of how/when the bulb turns off the voltage has equalized @~ 12v on each side when (a good*) alternator is rotating at idle.

* Have alternator shop tested

YMMV

[brokencase]

I wonder if your Hitachi works the same? I wouldn't mind the dim light so much if I knew the alternator would continue to charge if the bulb burned out. As it is I'm contemplating just getting one of the Titan alternators.

I'm pretty sure it works the same Brad. As you recall, I tested everything first outside the car. I clip leaded the alternator to a battery along with a 12v bulb to simulate the dash light. I then spun the alternator with a drill and the lamp went out. I also put the DMM across the battery and could see that the alternator was making voltage higher than the battery.
This confirmed that I had the connections correct and that the alternator was working.

Don't know what else I can say to help you out.

[DPDISXR4Ti]

As you recall, I tested everything first outside the car. I clip leaded the alternator to a battery along with a 12v bulb to simulate the dash light. I then spun the alternator with a drill and the lamp went out. I also put the DMM across the battery and could see that the alternator was making voltage higher than the battery. This confirmed that I had the connections correct and that the alternator was working.

I'll go bench test my spare 110A alternator as you detailed above and back on page 6. For the lamp connection, did you just run the other end to the battery GND?

I also just ordered a 91K-mile 130A Hitachi. At $35 to my door, I figure it's worth messing with, in case there's some unforeseen difference. And in the end, I wouldn't mind having the extra amperage available.

I drove the car ~20 miles today and it's all working well, save for the pesky dimly lit battery light. In daylight, you can't even really tell it's lit - got me wondering if perhaps the problem pre-existed! My working theory is that there is some marginal wiring issue on the car and the Mitsutachi alternators are more picky about setting off the light.

[DPDISXR4Ti]

"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."

In my rush to find a simple solution, I glossed over the fact that the circuit failed this ^^^ test - the light is dim with the connector disconnected. I bet I could replicate this with the original Bosch. Is the alternator even involved in this test? If this is indeed good diagnostic info, it would seem I have an issue with the wiring or the instrument cluster.

And confirming with data, with the quick-connector still disconnected from the alternator, probing the back of the circuit board, I get 7.8V on the blue D+ #61 side of the bulb and 12V on the Gnd side. This is similar to the running data I got, albeit that was a little higher since I was charging at that point (13.9 & 8.8V).

But circuit #61 checks out good end-to-end, at least from a resistance standpoint. Perhaps when more current gets passed through the issue gets raised? I wish I understood this stuff better - I only know enough to be dangerous.

[brokencase]

For the lamp connection, did you just run the other end to the battery GND?

No. You will need a test bulb to bench test the alternator.

As I said over and over. One side of the bulb goes to +12v. The other side of the bulb goes to the lamp connection on the alternator. With the alternator NOT spinning the bulb will glow. When the alternator spins the Lamp connection side will rise to +12v. You will then have +12 on both sides of the bulb and it will go out.

Lets review the alternator bench test...

On the garage floor we have...
A car battery
An alternator
several big clip leads
a drill rigged with a socket that can spin the alternator
A DMM
a 12v light bulb. Preferably with two wires soldered to it.

1) connect the case of the alternator to the battery negative terminal with a clip lead (or jumper cable)
2) connect the output stud of the alternator to the battery positive terminal with a clip lead.
3) connect the S (sense) of the alternator to the battery positive terminal with a clip lead.
4) connect one side of the 12v light bulb to the alternator LAMP , the other side of the bulb to the positive terminal of the battery. Note that the bulb glows at this time.
5) hook up the DMM to measure the battery voltage.
6) spin the alternator with the drill. Note that lamp goes out. Note that voltage across battery rises slightly.

[zxr250cc]

Hi all,

I am reading the '86 year electrical troubleshooting manual page 52 and it mentions the idea that the starter relay ground and connections could affect the light being on. I am sure you have checked these to be clean and well grounded. Yes? If this seems dumb, sorry, trying to help. This is the XR book but the idea would apply to any vehicle.

Cheers

[DPDISXR4Ti]

Thanks for the thorough explanation of the bench test Dean. When I get a chance I'll cut and paste that as a stand-alone thread in the FAQ section for future reference.

In the mean time, overnight I thought more about how I could be getting 7.8V on the circuit 61 side of the bulb with the alternator quick-connector disconnected and the key in the on position. You may recall on my earlier running test I got 8.8V at this location, but the test with the connector disconnected made it more clear to me. Clearly this crappy voltage has to be coming from the Engine Run Relay which circuit 61 passes through on pin 86. I'm thinking either the 12V+ or Gnd to that relay must be compromised. Page 23 in the 1988 EVTM.

[DPDISXR4Ti]

Today I tried to focus on everything coming in and out of the Engine Run Relay. And yes, I had already tried another relay.

Integrity of ground from relay socket pin 85 to G1005 is good.
Integrity of G1005 ground to battery and an assortment of ground locations (including alternator case) is good
Integrity of Lamp D+ circuit through pin 86 in either direction is good
Incoming 12V+ 30-2 circuit to pin 30 on relay is perfect. Literally exactly the same 12.55V as measured at the battery.
Fuse #8 to relay pin 87 is good

I don't know what else I can check there - it all tested fine.

So then I thought of one thing I hadn't checked - output of the Lamp circuit right at the alternator with the engine running. It measured 9V, essentially the same as the 8.8V I measured the other day at the back of the cluster. Neither 8.8 or 9 is enough to shut the light out. Given that both Mitsubishi alternators have operated the same way - and one of them was a recent rebuilt unit - I'm wondering if they just both work that way?

At this point I await the arrival of the 130A Hitachi alternator. I'll bench test all 3 and see what I come up with.


-

[DPDISXR4Ti]

I got some counsel from a guy in Scotland on one more test to do.

What I would do to confirm that the warning light circuit is working properly is disconnect the alternator harness connector and use a length of wire to link the warning light terminal of the connector to the alternator main power supply post. That will apply +12V between the two components, resulting in 12V across the relay coil, making it switch on. And 0V across the warning light bulb, making it switch completely off. If that check out OK you know the problem has to be the alternator (Note, this is a "test mode" only as without an input to the Lamp circuit the alternator doesn't charge. And also, with the key off, the battery light is on full bright.)

On to the test.... As expected, the battery light went out, confirming that the warning light circuit is working as it should. His conclusion is that the alternator is the problem. I didn't even get into the fact that I've had two of these alternators operate in the same way and one of them is a rebuilt unit.

The 130A Hitachi is scheduled to arrive Tuesday. My bench is cleared,

[DPDISXR4Ti]

Nothing like a herniated disc to slow down this project, but I was finally mobile enough today to do my bench testing.

Group 65 (truck) Battery measured 12.63V at test start.

The 110A Mitsubishi made 12.95V when spun up and the bulb went right out as it should. Monitoring the voltage on either side of the bulb it measured 12.95V, as it should.

The 130A Hitachi made 12.75V when put under the same test conditions and otherwise operated just like the Mitsubishi. Given the minimal RPM's I was spinning, I think it makes sense that the larger alternator would take some more effort to get going and so it only just started to make charging power.

Both alternators passed the diode test just fine.

An observation... Checking the voltage on the Lamp circuit on the alternator side with everything connected to the battery but not spinning, I get .75V, essentially the same as the .87V I observed in the car. I had thought that the .87V value may have indicated something weird, but apparently not.

Note, a battery powered impact gun or drill won't likely give you enough spinning velocity to get the alternator to start making power. In fact, at low speeds you may see the power drop across the terminals, especially on the larger alternator. I used a 1/2" chuck electric drill that is about 45 years old, so not a speed demon. I was able to use my 1/2" drive 24mm socket stepped down to 3/8 and then 1/4" so that it would fit the 1/2" chuck.

In short, the alternators check out fine, and I suspect the other 110A Mitsu that is currently installed will also check out fine. So the million dollar question is, why is the Lamp circuit making proper voltage on the bench but not when installed in the car?

[Ed Lijewski]

It would be hilarious if your fuse block mods had some involvement in that matter...

YMMV

[DPDISXR4Ti]

It would be hilarious if your fuse block mods had some involvement in that matter...

Oh, I've absolutely considered that. From my earlier tests there was zero voltage drop from the battery through the fuse block and on to pin 30 of the Engine Run Relay. There's a miniscule .02V drop across the main B+ circuit that goes through the 200A fuse in the fuse block; that's actually an improvement from what had been there before with the 35 year-old factory wiring.