Alternate Alternator Upgrade - Nissan/Infiniti

[DPDISXR4Ti]

Some new insight....

AUTOSPARK said:
Your earlier voltage measurements on the car show that there is no voltage output from the warning light terminal of the alternator.

Whether it's been 7.8, 8.8, or 9V, those are all essentially the same, and coming from the car side of the equation. This diagram shows how a potential voltage divider circuit is created as a result of the warning light bulb and the relay coil being connected in series.

https://www.hyundai-forums.com/cdn-cgi/ ... ng.473464/

So basically the warning light in the cluster is not seeing ANY output from the Lamp circuit of the alternator. Good God, could it be as simple as a lousy alternator case GND? Next step is to run a dedicated GND from the alternator case directly to the battery. If that doesn't solve it, I'll essentially replicate the bench test on the alternator in the car.

[brokencase]

I can't believe that Brad. Just the dang bracket and mounting gets the alternator to ground.

Can you confirm a good motor to chassis ground strap?.

[DPDISXR4Ti]

I can't believe that Brad. Just the dang bracket and mounting gets the alternator to ground.

You're right Dean, but first thing I did any way was ran a heavy jumper cable between the alternator case and the battery ground. No change - battery light goes dim once the engine is started and 9V measured at the warning light circuit. It would have been hard for the alternator case to have had a bad ground, but I had to verify.

So then I went with the idea of basically replicating the bench test on the car by eliminating the bulb in the instrument cluster from the circuit and creating a temporary battery warning light wired directly off the Lamp circuit at the back of the alternator. Just like on the bench, the other side of the bulb goes right to the battery 12V+. Bam, I start the engine, light goes out and 14.5V registered at either side of the warning light. The cigarette lighter voltage gauge also shows the battery is charging.

Not surprisingly, the battery light in the instrument cluster continues to glow dim once the engine is started. I'm sure it would be showing 9V at the back of the cluster as it has before, still looking for that 14.5V.

So we've verified that the alternator is totally fine, right? But I'm at a loss as to what else to check on the car.

[dimswits]

So we've verified that the alternator is totally fine, right? But I'm at a loss as to what else to check on the car.

You've found that the alternator and warning lamp circuit work properly in your "bench" setup, while it does not when patched in to the car, so consider how the alt lamp/field coil circuit works...

When the alternator is not spinning, battery voltage is fed to the field coil terminal (D+) through the warning lamp, energizing the coil and illuminating the lamp. Once the car is started and the alternator is spinning, the voltage regulator back-feeds the generated voltage out of the D+ terminal. At this point the lamp is getting battery voltage on one leg, and alternator voltage on the other. These two voltages are supposed to be equal, in which case there is no potential difference across the lamp and it goes out.

So what you are seeing is that at least with respect to the charge lamp, battery voltage and alternator voltage are NOT equal, so your lamp is staying dimly lit. The question you need to find the answer to is why are those two not equal?

You say you are measuring 9v at the warning lamp circuit. How did you take that measurement? Was that from one or both of the bulb terminals to ground? Or was it across the bulb terminals? You should be seeing 0V across the terminals, and you should be seeing ~14.4V from either terminal to ground.

[dimswits]

So basically the warning light in the cluster is not seeing ANY output from the Lamp circuit of the alternator. Good God, could it be as simple as a lousy alternator case GND? Next step is to run a dedicated GND from the alternator case directly to the battery. If that doesn't solve it, I'll essentially replicate the bench test on the alternator in the car.

You should be able to check this pretty easily using a different feature of the car. The voltage on the D+ terminal that is present when the alternator is spinning is used to energize the engine run relay. When the engine run relay is energized, you will not be able to pop the fuel door or unlock the hatch by way of the push button. You can start the car and leave your doors unlocked and try to open the hatch with the pushbutton. If you can, you are not getting the expected voltage OUT of the D+ terminal (or the relay is dead).

In fact, you might consider pulling that relay while the car is running and see if your alternator lamp goes out...

[dimswits]

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.

Having just read this I definitely think your next step is to pull the engine run relay out. I am assuming the 8.8V reading is on the alternator side of the bulb.

The 1989 EVTM also shows a splice out to the "parking lamp relay" from the battery side of the alternator lamp. The 1988 EVTM (for early built cars) shows no such splice. In fact, the circuit in the 89 evtm makes no sense to me, so I think it might be an error.

Pull that engine run relay.

[DPDISXR4Ti]

In fact, you might consider pulling that relay while the car is running and see if your alternator lamp goes out...

Thanks for chiming in D. I should have thought of this ^^^ idea and will give it a try (see below). I recall being surprised when I took a look at the schematic and found the D+ circuit went through the Engine Run Relay. I thought it was just going to be a simple straight shot to the cluster.

That said, today I decided I needed to make sure I hadn't created an issue with all the other work done on the car and so the original Bosch alternator went back in. It worked fine, 14.2V across the battery terminals, 14.15 at the D+ terminal, and no more dim battery light.

Undeterred, I immediately pulled it out and started putting the 130A Hitachi alternator in. I hit a couple snags and so didn't get it finished tonight. Hopefully tomorrow. If the dim battery light returns I'll try pulling the relay. Watch this space...

[dimswits]

That said, today I decided I needed to make sure I hadn't created an issue with all the other work done on the car and so the original Bosch alternator went back in. It worked fine, 14.2V across the battery terminals, 14.15 at the D+ terminal, and no more dim battery light.

Undeterred, I immediately pulled it out and started putting the 130A Hitachi alternator in. I hit a couple snags and so didn't get it finished tonight. Hopefully tomorrow. If the dim battery light returns I'll try pulling the relay. Watch this space...

Given this, and the fact that your bench test on the Mitsubishi alt worked as expected, leads me to believe that the issue is with a difference in operation of the voltage regulator on the Mitsu alt versus the Bosch.

Brokencase mentioned earlier that he would not tap the "sense" signal on the Mitsu alt right off of the B+ stud, but rather move it to the battery. If you pull up the charging diagram for a 2005 Altima or G35, you'll see that the D+ signal is routed similarly to ours (except through an LED and resistor in parallel, with a logic circuit in some of them). The "sense" signal is routed to the power distribution and is hot at all times.

The fact that it's hot at all times tells me it is most likely used as a reference signal for the Voltage Regulator to use in its logic (rather than say exciting the field coil). Likely it is sampling the difference between what is reading off of the B+ post and off of the sense signal. Perhaps when not spun up it is also sampling the difference between what sense and D+ are reading. Using these, maybe it is deciding what to put out on the D+ line.

This is a long way to say I agree with brokencase that you should move the sense wire off of the B+ post and over to your battery, or perhaps over to the +12 feed into the alternator lamp.

[DPDISXR4Ti]

This is a long way to say I agree with brokencase that you should move the sense wire off of the B+ post and over to your battery, or perhaps over to the +12 feed into the alternator lamp.

I've already tried that and saw no difference.

But, never mind that, you're a genius! I just got the Hitachi installed and started the engine. 14V across the battery terminals but we're back to 8.8V at the B+/Lamp circuit and a dim battery light. So I took your idea and pulled the Engine Run Relay... Dim battery light goes out and now I'm getting 14V at the B+.

I see that I need power across the Engine Run Relay to be able to open the fuel filler door and hatch. I don't care if I can still do that while the car is running down the road. Can I just jumper 30 to 87A and call it done?

[DPDISXR4Ti]

I see that I need power across the Engine Run Relay to be able to open the fuel filler door and hatch. I don't care if I can still do that while the car is running down the road. Can I just jumper 30 to 87A and call it done?

Yes I can.

NissanAltRelayNoMore.jpg (321.69 KiB) Viewed 3061 times

I even got sensible and fused the jumper. Tested and works fine. I forget to check it but I assume I can now open the fuel filler door while the engine is running, but who cares? Hatch locks as it should when the doors are locked.

I have no idea why Dean's car worked as-is with the Nissan alternator and mine did not. Mine is an early car - as you alluded to, maybe there's some minor difference between the early and late cars that makes a difference? The relay is the same, so that's not it.

[DPDISXR4Ti]

Since I had both Nissan alternators in and out today I thought I'd post installed pics, taken from below, looking up. Here's the 110A Mitsubishi. It's a little easier to fit and deal with in a few ways. Unless you're adding something that has a big power draw (electric power steering anyone?) this one is probably fine for most. Factory original adjusting bracket was used for both installs - I just took the offset out of it by flattening it in the vise.

NissanAlt110Mounted.jpg (279.17 KiB) Viewed 3059 times

And this is the 130A Hitachi. While it's very similar in mounting to the Mitsubishi, there are a number of little things that are different. The case is larger so I had to reverse the adjusting bracket to get it to work. Even with that I had to put more spacers under it than I was comfortable with. The shaft is even shorter than the Mitsubishi; as a result, my previously machined pulley would not work. I came up with an alternate pulley for testing purposes but it's designed for a narrower belt, so not a permanent solution (and I'm not going with a smaller belt on a larger alternator). Between these two things, I decided to stick with the Mitsu for now.

NissanAlt130Mounted.jpg (243.87 KiB) Viewed 3059 times

One other note I'll add here, if only for myself... The Hitachi needed a .330" spacer while the Mitsu needed .350".

[Ed Lijewski]

I see that I need power across the Engine Run Relay to be able to open the fuel filler door and hatch. I don't care if I can still do that while the car is running down the road.

I even got sensible and fused the jumper. Tested and works fine. I forget to check it but I assume I can now open the fuel filler door while the engine is running, but who cares?

No biggie fer shure, but it's verrrry common, for driver and or passenger, to inadvertently brush against the fuel door solenoid switch and not notice that it actuated.

YMMV

[DPDISXR4Ti]

Here's the solution that a Scotsman came up with for me. He too had come to the conclusion that there was an incompatibility between the car and the Nissan spec alternators solely with respect to the warning light circuit. I was about to try this until I came up with today's solution of just eliminating the Engine Run Relay entirely. If the function of the Engine Run Relay was more important I would have needed to go this way.

Screenshot (6).png (155.99 KiB) Viewed 3056 times

To modify the circuit you need a 12V change over relay. A change over relay has 5 terminals marked 85, 86, 87, 87a & 30.

You connect the 86 & 87a terminals to an ignition 12V supply.

Connect 87 to ground.

The 85 terminal connects to the alternator's warning light terminal.

And 30 connects to the wire leading to the car's charge warning light and engine run relay....

When the engine is off the alternator's warning light terminal outputs a ground, which energises the changeover relay. The relay switch moves to the normally open position, linking the 30 & 87 terminals. That grounds the car's warning light circuit, illuminating the charge warning light.

When the engine is running the ground on the alternator's warning light terminal switches off, which de-energises the changeover relay. The relay switch moves to the normally closed position, linking the 30 & 87a terminals. That applies +12V to the car's warning light circuit, which will completely switch off the warning light and switch on the engine run relay.

[DPDISXR4Ti]

The Mitsu/Nissan alternator has been working fine. I love the fact that when I was driving the car the other day with the lights on, HVAC on, and wipers going, the voltage barely blinked and stayed right around 13.8V.

Just one weird thing happened though.... When I got home the other day I left the car outside to unload a few things. After unloading - 10 minutes later - I started it up to pull into the garage. The battery light was on full bright, but yet voltage indicated ~13.8 as it should. I blipped the throttle a couple times and pulled into the garage with no change in the battery light. I've since driven the car with a couple stops and my wife has it out right now - totally normal operation.

Do I just pretend it didn't happen? So far that strategy is working.

[Ed Lijewski]

Are you reading V via the cigarette lighter?

YMMV