2G Alternator charging low

[v8s_are_slow]

So I've had this issue ever since doing a battery relocation to the rear. I have some 0 gauge wiring from the battery to distribution block under the hood, and another straight to the alternator. I have a 165A alternator, but still, it only wants to charge between around 12.5-12.7 volts or so. I have NOT upgraded any wires to/from the 4 pin plug that goes on top of the alternator. I purchased some 8 gauge wire if that needs to be upgraded but if so, which one would need to be upgraded, and where would it go? I have multiple grounding points, alternator was tested twice, stock alternator does the same. I had also cut pin 33 at the ecu at the direction of Drew Jones (for those that know him anyway). Any input??? Thanks!!!

 

[Stapl3]

How is the grounding wire at the battery ran?

 

[luv2rallye]

I assume you have the 2gT. Your alt 4 pin connector's pin 2 "S" (red wire) MUST go directly "on it's own separate wire" through a small fuse ONLY to the REAL battery positive post (NOT to some wire that connects to the battery positive post OR to anywhere else). This is the alt's sense wire (hence "S"). The alt will output whatever it has to to make the end of that wire be 14.4V. That's why it must go directly and only to the battery positive post! Using the big battery positive cable (which is probably what you are doing) will drop voltage and so the voltage at alt pin 2 (S) will not be correct.

Right now that red wire goes to the 40A fusible link in the engine fuse box which connects to the fuse box's buss that goes to the old battery's positive location.

Procedure: Disconnect the battery. Now cut that red wire right at the alt and tape up its harness end so it can't touch anything (it will be hot when battery is connected). Connect a new wire (for small current) to the other end that goes into alt pin 2 "S", and run it through a small fuse (eg. 1-5 amp) all the way back to battery positive post. [Note: The "S" wire is a voltage sensing wire only - almost no current flows through it.] Reconnect battery. Now the alt will output what it has to to try to keep the battery positive post at 14.4V.

 

[trustedmaniac79]

Luv2rally, I was having same issue as the OP was, so I did what you explained in the previous statement you posted.

After I did this my battery light was on & if I pushed throttle it would drop rpm before revving any at all & stumble, but my voltage was at 14.3v at idle. Why is my battery light on from doing this like you described?

I didn't think the battery dash light was on that wire or even should kick it on just from running a different wire to my battery. Also if I unplug my alt 4 pin connector the light goes out but then it doesn't charge at all.

It's a 98 Spyder GS with battery relocated to the trunk & I have replaced the alternator wires with 1 4 gauge wire going to fuse box & then to a power distribution block, that's where all the wires that would normally be on battery positive post is connected & I have 1 gauge wire ran to the battery from power distribution block. I've upgraded all the grounding wires from the engine to firewall & on the battery in the trunk I have 2 1 gauge ground wires just ensuring I have adequate grounds.

 

[luv2rallye]

Is this the 2.4L engine?

Don't know why your battery light is on as it is on a different wire (alt "L" pin 3 of the 4 wire connector, black-yellow but sometimes blue if no generator relay). Did you accidentally mess with this wire or the generator relay? What voltage do you have on this wire at idle and non-idle?

Is the 14.3v right on the battery or where are you measuring?

Unplugging the alt 4 pin connector will always make the charge light go out and not charge the battery since that disables the alt's field coil (which makes the alt operate).

 

[trustedmaniac79]

It is the 2.4L 5 speed
Yea I don't understand why it is happening either. I cut the pin 2 red wire on the 4 pin alt connector & ran the wire from it to my trunk & I have a inline fuse wired in with 5 amp fuse just before the battery then connected to the B+ post. With it like that it charges at idle 14.1-14.3v but the batt light is on & the brake light also, plus the throttle is dropping down 300-400 rpm's when pushed before it will increase & then it stumbles for a sec. With it hooked up how it was from factory I have no issue with my throttle or any driving/idle problems at all & no dash lights on but it only puts out 13.2v at idle & after it warms up to operating temp it goes down to 12.6-12.8v & while driving it nevers goes over 13.1v. also with it hooked up with the "S" wire connected straight to the B+ post & the light is on the dash of I unplug the 4 pin connector & start car the batt light & brake light aren't on anymore but the alt isn't charging either. Which is the opposite of how it is supposed to function

 

[luv2rallye]

Are you sure you cut and re-strung only the correct pin 2 wire? Because if you mistakenly (or somehow) also connected the pin 3 wire to it, you'd get the result you describe: correct charging (14.3v at battery), but the dash batt and brake lights will then be off (because +12v is then on both sides of them).

Note: The alt needs +12v on pin 3 (alt field coil) to turn itself on. This is normally provided THROUGH the batt dash light (without turning that light on - just the +12v on pin 3 does it). When the alt isn't working that pin is tied low (to ground) which then turns the batt dash light on. But if pin 2 and 3 are somehow mistakenly tied together, you'd get the case in my first paragraph.

Another note: The 4 pin inline connector can be confusing as to which wire is pin 2 (eg. is pin 2 the 2nd one from this end or the other end?). Plus wire colors fade or look different with age. The correct pin 2 wire is the one between the white and black/yellow (blue w/o gen relay) wires. Not between the black/yellow (blue w/o gen relay) and green wires (green is on the end). Be careful of wire fading especially on the white wire.

 

[trustedmaniac79]

Wouldn't unplugging the connector also turn on battery light, since there's no field?

I appreciate you explaining everything in detail & ensuring I know how to properly count the connector pins
& everything ty. But lets speed this up a lil, I'm actually a mechanic by trade & have been doin this for the past 24 years, but I also know nobody knows everything when it comes to working on cars. So I'm decent with electrical & reading electrical diagram, enough about my background. I was at a loss on this & figured I might be looking at it incorrectly or something I'm not seeing, so again thank you for replying back to this.

Now to answer your questions, no I've never have cut any of the wires on the 4 pin connector until I did the pin 2 red wire earlier today. Looking at the back of the connector wire goin into the plug left to right for counting pin locations, pin 1 white pin 2 red & the pin 3 I think is blue & don't ever remember what pin 4 is. I've checked make sure there was B+ voltage on pin 2 & on pin 3 & there's 13.9 - 14.3 volts at idle on both.
I'm measuring the voltage using dmm at the alternator stud & I've checked it at the power distribution block & on the battery post & using evoscan each time I haven't driven it yet cause I wanted to figure out what's goin on & not cause potential other problems by driving it like that.

When u turn the car off the light comes on cause of no field, alt not charging the battery it comes on. So why would unplugging the connector turn it off? It wouldn't have a field similar to the previous conditions I mentioned. Or am I thinking about it incorrectly?

I would think unplugging the connector would turn on idiot light informing driver battery not charging whether it's just unplugged or an actual fault in the charging system.
I forgot to mention I do not have the alt relay on this vehicle

 

[luv2rallye]

No disrespect on wire counting. It's easy to not know which end of a 4 inline wire connector is pin 1. I do it all the time since it's hard to know which wire side of the connector is the one that matches their diagram (which end you're looking at). And their male/female refer to the pins inside which you can't see, as well as their physical outside connector male/female outline is usually totally confusing. So I find it easier to locate the wire by identifying the wires on either side.

Pin 4 is green (although it may look different due to age).

The reason the batt and brake lights go out when you unplug the connector is because that completely removes the connection to one side of them (which is pin 3). When connected, pin 3 high causes the alt to turn on (provides alt field coil voltage) and the lights to go out (because +12v is on both sides of them). With pin 3 low (near ground) the alt turns off (no alt field coil voltage) and lights turn on (ground is now on one side and +12v on the other).

See wiring schematic here: https://www.dsmtuners.com/attachments/alt-diagrams-2gt-jpg.289997/

 

[trustedmaniac79]

I appreciated the thorough explanation of the pin numbering cause I could've not had any idea, so ty. But the lack of voltage from unplugging on pin 3 would be similar to low or no voltage on it. Or does there have to be voltage on one of them - not the other is how it turns on? Cause they turn on when vat is KOEO so then there's no field being made either, or does it use one of the wires for path to get to a ground source & without the connector plugged in it has no path & that is why they go out?

I just don't understand why it's on right now but it wasn't before & my voltage was borderline acceptable when it was off & now with me driving I stay at 13.6 or higher.

 

[luv2rallye]

What is the measured voltage on pin 3 (with connector plugged in) when the batt light is on?

Also when on, are the batt and/or brake lights dimmer than they usually are?
And is the batt and brake lights a normal incandescent light or is it now an LED?

The light goes out when you unplug the A-03 connector because then there's no complete circuit for the light (see schematic). It doesn't matter if you have +12v on one side of the light if the other side is not connected to anything (no place for current to flow to).

 

[trustedmaniac79]

Just to update you I figured out why the battery light was on just so you know. But I'll be home shortly & post what it was. But now there's another issue that came back after I fixed the battery light being on.

Ty love2rally for your knowledge & assistance with this, I always find it beneficial to bounce ideas & theories off of other knowledgeable people when something isn't making sense instead of thinking I know everything, I don't or wasn't looking at it properly.

 

[trustedmaniac79]

I was thinking the light would've been grounded elsewhere was my reasoning for assuming it would come on if you unplugged it.

So turns out the small wire I used 20 gauge, you said to use smaller wire when saying how to do this procedure or that's how I interpreted it. When I had crimped the waterproof butt connector onto the wire I was running I obviously had broken several of the wires on the process from not having much room to get my crimping tool in the small space between alt/turbo/radiator. As for how I found it;

I knew it had to of been something I did/didn't do when doing this since it wasn't like it previously. So I retraced everything I had do. When I was taking measurements at the plug I used a probe piece that attaches on my dmm lead & it has a very small extremely short lil spike that penetrates the installation of the wire, cause I try to never use things to back probe a pin on a connector I've seen people f@ck them up before.

So with the limited space & everything I figured this would be best, now where I messed up or I would have caught it on my original measurements before I ever posted this is I assumed my crimped butt connector was good & it was easier to probe behind the butt connector from pin 2, which is exactly why I thought there was batt v on both pins. Actually there was not any on pin 2 from the wires breaking as I crimped it to red wire coming out of pin 2, I tested pin 3 same way but I was able to get almost directly behind the pin 3 terminal.

After I was checking everything I had touched or might have touched not knowing or realizing & found nothing I decided to do continuity test from the of the new "S" wire I added. So I used same probing attachment but did it at the firewall before going into the car & unplugged the alt connector & touched pin 2 from the front side of the connector & thee was ZERO continuity. I wanted to break something at this point for my overlooking the basics of diag. So I reran a different wire this time using 16 gauge wire & hooked everything back up & no more dummy lights on the dash.

But now I have the same damn problem I was having originally & only getting 13.3v at the most when 1st starting up the car while cold, once warmed up idle V goes down to 12.7-12.9v & while driving never got anything above 13.1 which is actually worse than before I did this but just slightly. I'm starting to think my alt isn't working adequately, cause the ONLY time it would put out decent V was when it couldn't sense anything on "S" line so that was its best attempt to get 14.4v on the "S" wire & it never even hit 14.4, it got close once or twice at 14.1 but mostly just mid to high 13's. Or should I look into something else?

 

[luv2rallye]

I was thinking the light would've been grounded elsewhere was my reasoning for assuming it would come on if you unplugged it.

If you look at the wiring schematic (which I think you've learned you must ALWAYS first do to understand the operation and what wire does what [or at least goes where], BEFORE doing any wiring CHANGES, tee, hee), you'll see the light is turned on or off by switching the negative side of the light to ground or not. And the switching is done INSIDE the alt on pin 3 which it HAS to be, to indicate whether the alt is outputting or not. You probably assumed they were switching the positive side which is incorrect and a common mistake.

So turns out the small wire I used 20 gauge, u said to use smaller wire when saying how to do this procedure or that's how I interpreted it. When I had crimped the waterproof butt connector onto the wire I was running I obviously had broken several of the wires on the process from not having much room to get my crimping tool in the small space between alt/turbo/radiator.

Yes I probably shouldn't have said to use a small wire even though it will carry a small current (which is why I said it). You need a minimum size wire (say 16) just to handle all the vibration, crimping, and abuse. Even the Mitsubishi Service Manual shows a 14 gauge wire on pin 2.

But now I have the same damn problem I was having originally & only getting 13.3v at the most when 1st starting up the car while cold, once warmed up idle V goes down to 12.7-12.9v & while driving never got anything above 13.1 which is actually worse than before I did this but just slightly. I'm starting to think my alt isn't working adequately, cause the ONLY time it would put out decent V was when it couldn't sense anything on "S" line so that was its best attempt to get 14.4v on the "S" wire & it never even hit 14.4, it got close once or twice at 14.1 but mostly just mid to high 13's. Or should I look into something else?

Well I suppose it could be a bad alt (or weak battery), but the fact you used to get high 13's says it used to at least output something (since battery nominal voltage is 12.6v). I assume you have the battery cable terminals clean and tight.

What is engine running voltage now on pins 2 and 3 at idle and non-idle?

Also make sure pin 1 is not anywhere near 0v or the alt is forced to output no more than 12.5v.

And what is the voltage on the alt's high output current large wire terminal AND right on battery positive post? This so we can see the voltage drop on the way to the battery.

 

[trustedmaniac79]

So I ran to the store a lil bit ago & now even after it's at operating temp it's at 13.7v idle & while cruising it was fluctuating from 13.4- 13.9v. that wasn't with any lights/ac/ radio on just my cooling fans running. I didn't change anything since driving it yesterday. But I'm going to leave it as is my battery light is off & I'm within acceptable V.

To follow up with your question about the voltage drop from Alt output stud to the B+ post is 0.2V-0.3V, which isn't ideal but not that horrible with battery relocated to the trunk. Also battery is only 2 months old optima red top & no the battery isn't weak or getting discharged, I haven't had to jump it or put charger on it at all, to answer your question.

 

[luv2rallye]

Yes, leaving it alone the way it now is sounds like a good solution.

If you get a chance though I'd still like to know what the engine running voltage is on alt pins 2 and 3 at idle and non-idle (just to make sure it's reasonable)?