Voltage drop during acceleration... '96 3.2l sohc
 

So the other day I noticed my dash lights dimming during acceleration and sure enough, I glanced over at the gauge on the dash and it would drop to 12 while I accelerated, once I took my foot off, the reading went back to normal...I have never seen this before, on anything.......Its a 1996 (10/95) Trooper 3.2 sohc with 181k miles on it. Also has a brand new alternator from NAPA that has less than 150 miles on it. I took it to NAPA and had them run an electrical test on it, it passed on everything from the battery to the alternator... Everything is working just fine, just the movement on the gauge.Also I did notice that the lights dim/gauge moves in rythym with the turn signal. That I have seen before on other cars, is this connected to the acceleration things too?Any guesses?

The alternator should be producing more current when accelerating because of the higher RPMs. The opposite of what is happening to you.
Does it have an external voltage regulator or is it in the alt?

Im pretty sure that it is an internal regulator...

I cannot be certain until I read through my repair manuals, but are most cars of this age and newer all internally regulated?

Yes, usually they're internal now, just thinking of possible answers to your problem.

My trooper has the same problem. Did anyone find a solution?

NO...

But, it never really caused any problems.

I guess its more of an anomaly than a real problem.


Did yours ever become an issue? I cant say because I ended up selling mine.

Seriously, lots of people rest their foot on the clutch without realizing. It's a one way ticket to a burned out throwout bearing, not to mention new clutches much too often.

I have the same truck and the same thing happens. I did some research and found this is normal. The ECM tells the alt to stop charging during hard acceleration to lessen the load on the engine. I should have looked this up before pulling the alt and testing it.

Voltage drop during hard acceleration- '97 Trooper
 

I found this on another site. Does anyone know if this tech bulletin also applies to the '97 model (3.2 LX)? I just had new alt installed and they said the drop is normal?


1996 Isuzu Truck Trooper V6-3165cc 3.2L SOHC (6VD1)
SB96-04-L002
ISSUE DATE
FEBRUARY 1996
GROUP
ELECTRICAL
1996 TROOPER (UX) AND RODEO (UC) VOLTMETER NEEDLE
DROP DURING HARD/QUICK ACCELERATION
AFFECTED VEHICLES
1996 Trooper (UX) and Rodeo (UC) models.
SERVICE INFORMATION
On all affected vehicles, the instrument panel voltmeter needle will drop during hard/quick acceleration. This voltmeter needle drop is normal and is not indicative of a condition requiring repair.
1996 vehicles are equipped with an alternator that is designed to stop charging during certain engine speed modes in order to lessen engine load. At idle, the alternator will output approximately 14.3 volts. During a slow/steady acceleration, the alternator will remain at a 14.3 volt output. However, during a hard/quick acceleration, the alternator output will drop to 12.7 volts. The alternator will continue this 12.7 volt output, until the Powertrain Control Module (PCM) detects a drop in engine speed, at which time, it will return the alternator output to 14.3 volts.

I just wanted to agree with Trooper012's information. I have been a mechanic for 40+ years and still own a bunch of Troopers. I was going to give the same information. I think when they went to the 3.5 motor they dropped this idea as they had more power. The voltage was controled by the TPS and manifold vacuum to give that little extra power and once the load was dropped everything goes back to normal.

I forgot to add this is memo is from 93-96 Troopers and Rodeo's.

randomorbit3,
My Trooper is a 1997 and it does the very same voltage drop in the tech bulletin I posted earlier for the '93-'96. Should I be concerned at all because it is a 1997? Not many people seem to know much about these guys.
Thanks

Trooper012,
As far as I am concerned, NO!!! As long as the voltage gauge goes back up once you ease back on the gas pedal. If that is not the case then I would be upset. I log it into my brain as a Isuzu thing. hahahahahaha Supposed to be a joke.

Let me know if this puts you at ease :)

randomorbit3,
That is great news. The voltage does go back up as soon as I ease of the gas. Thanks a lot for the follow up response!!!

I thought you might like to know the reason they did this was to give the old girl a wee bit more pep under hard acceleration. Trust me it is much worse in the older Troopers, like my 1991 Trooper with the 2.6L 4 cyl. engine. Thank the Lord it has the 5 speed and not a automatic for I might have to let a semi pull out first ;)

Happy I was able to put you at ease.

My solution
 

My solution to the way the vehicle operates is to turn on the lights when I want the alternator to keep operating.

You really do not need to keep the lights on. The ONLY time it should drop is under HARD acceleration and after that it should go back to charging. You will find that using the heat or a/c will do the same thing. Or just leave it alone as it IS working the way it should. What you need to know is that even though you do not see the gauge showing a charge it is still charging because you have a volt meter instead of a amp gauge.

Any other questions let me know and I will try to help. Or just say HOWDY from time to time :)

yes ... and there is an after market RPM limiter that can be istalld to protect the older 95 and older 3.2 dhoc from over rev during free neutral drop conditions.

Another transmission comment to answer a voltage question... what an ass-clown

johnny5ive,
You know I NEVER heard of a REV limiter being used for neutral drops. I always thought they were for saving a engine on hi RPM shifts with a stick tranny. I think I might have to take another tranny course for I must have missed something. Only jerks will neutral drop a automatic and not even be thinking of the damage being done to the tranny, the drive line and the rear. I am amazed someone would show their intelligence this way on a forum.

Well they are right about one thing. After a while of doing hole drops the vehicle will not be on the road and we ALL will feel MUCH safer out there. I can not wait to see what their response will be to my comment :)