Charging system Problem !

[HADI-ZR1]

I noticed that the needle goes to about 11-12 volt during stop or 900 RPM.
the weather these days very cold about ~ 4 c. night.
I changed my alternator before year with new one!
when the engine runing in normal codition say above 1000 RPM , the voltage goes and stay ~ 14 V.

q: is it possible IF the battery is weak ,even with engine runing the voltage can be drop as my situation??! :icon_scra
where is the problem you think guys?
GUess why i post this thread in Parts wanted??









I WAS SMOKING! http://i128.photobucket.com/albums/p183/hadi-zr1/rofl-1.gif , But i swear of god its truth what my eyes seeing at gauges!

[tomtom72]

I don't think that the dash cluster gauge is percise.....what I'm saying is that I doubt that it can be used as a diagnostic tool.

To determine the system's actual performance or to actually see what the various voltage outputs are in various situations, you need to either use a volt meter hooked up at the alternator's output terminal or maybe at the battery terminals or hook up a scanner and scroll thru the readouts till the alternator's output is displayed. I don't think that the gauge was meant to be any more than a warning that there might be an issue developing with the charging system...ya know the gauge was not meant to be used in place of a volt meter or a scanner.

:cheers:
Tom

[gbrtng]

I'm guessing the battery has one shorted cell. Find an auto parts store that has a battery tester and analyzer.

[WB9MCW]

I'm guessing the battery has one shorted cell. Find an auto parts store that has a battery tester and analyzer.

Another way I do it is to take a volt meter and move from one cell to the next and see how they add up --- I just stick the pos. probe right into the fluid and measure. Works great and you can find a bad cell easy this way. Been testing batteries for years this way --- you can even go cell to cell with both probes in the juice (except for the end cells)and measure each one by itself this way.:thumbsup:

[HADI-ZR1]

Bryan,
nice idea and info.! can you show us in details how to do that?

BTW, still my Volts needle dancing @800-900 RPM till this moment.
its 3:00 AM now, and my plane take off at 7:00 AM.

see you ALL and take care...:hello:

[jonszr1]

bryan thanks for thew cool tip . can this be used on any battery ie 6volt?

[gbrtng]

kinda tough to use Bryan's technique on a sealed battery.

[WB9MCW]

kinda tough to use Bryan's technique on a sealed battery.

That is correct you have to have one that allows you to access the acid juice -- no juice -- no can do the measurements.

It is simple to do on any battery (even 6v) that you have access to each cell.

Just dip you plus and minus in the juice and work across the cells. From cell to cell on a 12 v you should have 2 V for a 6 cell 12V battery.

You can do em individually or start with the neg and cell 1 and add em up as you work across em all.

Real easy to find the bad cell this way!!!

[HADI-ZR1]

Guys,
Again the car could not start, very week charging!
whats going on? when the RPM go up to 1000-1100 ,the needle show at 3/4 , when the engine goes to 900 RPM, the needle show at 1/4 !! :cry:
Took this picture just now before starting my car! its 2:00 AM , and still snow on him!:-)
http://i128.photobucket.com/albums/p183/hadi-zr1/DSC00594.jpg

[Paul Workman]

Hadi,

All of the common tests to isolate the fault have been covered, except for a possible excessive load problem. However, the alternator should be able to charge the battery at idle in normal circumstances, even at idle.

So, if at idle the (VOM) readings across the battery terminals are less than about 14.x (cold) or 13.7+ warm/charged, you may have a load problem IF the regulator is working...And that is the question.

My bet is the regulator is bad. If you're not comfortable with the mechanics of checking it out yourself, then let an auto repair shop diagnose it for ya.

Don't over-think this. Chances are it is quite simple (and I'll bet on the regulator - other data not withstanding).

P.

[HADI-ZR1]

Paul,
Do you mean the internal regulator inside Alt. ??

P.S. I just start the car from chargring Jumper, then i went to supermarket , diconnect the Bat + Termnel , then came after hour, then i start the car , and the needle stay at 14.5 V. its was strange, even with 900 RPM !!
Then drive the car for 10 min. every thing was fine, then again after i top the car and Engine goes to 900 RPM, the needle start to play up and down, 1/4 - 1/2 position ! :dontknow:
BTW, i change my Alterenator before year ago with NEW one!

[HADI-ZR1]

Ok here is the vid, this is between 900-1000 RPM.
P.S i have the larger pulley on Alt. ( could this be the reason? )

http://i128.photobucket.com/albums/p183/hadi-zr1/th_MOV00596.jpg (http://s128.photobucket.com/albums/p183/hadi-zr1/?action=view&current=MOV00596.flv)

[WB9MCW]

Yea Hadi you need some REGULATION -- now go to a good shop and confirm!!

See if this thread gets you to the bottom of it all -- Early C4 -- proly similar (wires and testing at any rate) for our Z at least get you on course for finding the problem.

http://forums.*************.com/c4-tech-performance/2189452-alternator-and-battery.html

Here is the tech tip for the later larger alternators my guess is the same as our Z

http://www.*************.com/techtips/viewsubtopic.php?SubTopicID=254&TopicID=2

Another c4 bench test alt thread

http://forums.*************.com/c4-tech-performance/1920013-bench-testing-an-alternator.html

there are a few things you need to know.
1. the alternator is a constant potential charging device. That means there is a preset voltage limit in the alternator voltage regulator.
The alternator tries it's mightiest to achieve that at all times.
2.When you first start the car, the alternator wants to get to that voltage, and it kicks in more field voltage to accomplish this.
The field voltage is a function of the voltage regulator based upon it's constant battery voltage sampling.
3.so, cold, the battery has sat all night, it's achieved it's lowest unloaded voltage, and then just started the engine. The voltage wire on the plug on the alternator feeds the sample voltage to the regulator (CHECK THAT PLUG) then if the voltage is lower, the reduced battery voltage biases the voltage regulator, and the alternator starts out at 105 amps. As the battery voltage comes up, the field voltage goes down, ending up with the load and the battery setting the alternator load at any given second.
4. The alternator generates heat.
a. the heat of the alternator is respective of the load.
b. Load is based upon battery voltage
3. there is a thermister in the regulator that reduces the amount of voltage sampled by the alternator, reducing the voltage and the load.
4. reduced voltage and load reduces the battery voltage when the car is hot. The hotter the alternator, the lower the voltage to a point. The battery could overcharge at elevated temps and sulfate excessively, so this is a good thing.
5. The alternator doesn't produce much output below 550 RPM.
6. The alternators don't do well at extremely high temps.
7. Notice the voltage cold, and the voltage hot. it may vary by 2 volts or more.
8. overhauled alternators may be compromised by the overhaul methods.
9. there are aftermarket methods of reducing the alternator temp.

Third thread >>>92 Vette

http://www.corvetteactioncenter.com/forums/c4-technical-performance/14883-alternator-regulator.html

4th Thread 89 C4

http://www.digitalcorvettes.com/forums/showthread.php?t=108875

the ******* are the block on our favorite forum that is blocked at the server level ---tis what it tis --- too bad for this because every now and then a link to that forum is in order for stuff just like this!!!

Well you can proly guess what forun it is and finger it out!!

GOOD LUCK HADI --- KNOWLEDGE IS POWER!!!

[Paul Workman]

I started this response and then got called away, and didn't have time to read all the responses. So, at the risk of being redundant...:rolleyes:

One of the classic failure modes of electronic stuff is due to heat fluctuations; usually failing when going from cold to hot (but not always). Since it worked normally for a while and then quit, my focus would be on the regulator at this point: either it is failing, or there is a connection associated with the alt that is intermittent.

The regulator varies a DC pulse width to the stator, thus maintaining the DC voltage to the "load". IF the regulator is breaking down when hot, OR the plug-in connector on the back of the alternator (or some other) is intermittent, then the regulator will not increase the stator current pulse width - especially at low speed - and the DC voltage "falls out of regulation".

RE That connection that drives/supplies the regulator: It is a connector on the back of the alternator, and if it is loose/corroded, the alternator output can be low, or erratic as hell, depending on the nature of the contacts. (I tried all my tricks to enlarge this schematic (from the FSM), but you'll probably have to save it and look at it outside this post to better see it.)

http://i185.photobucket.com/albums/x220/6PPC_bucket/Vettes/LT5chargingschematicrawJPG.jpg

__________________

All That Said... Now I'll tell ya what really intrigues me...That surging! The video shows the voltage fluctuations are in coincidence with an idle surging - not the surge as much as when the rpm falls off is when the voltage drops "out of regulation". My point is, there is a chance it is not the regulator or the alternator per se', but a combination of the rpm surging/fall off that is coincident with the voltage dropping out of regulation at low rpm (a FACT we see in the video clip...a very helpful video clip too, I might add!:thumbsup:), aggravated by the under-driven alternator!?

Bottom line: I'd try to eliminate a few things first-

First I'd want to eliminate that surging at idle (usually due to an air (vacuum) leak). That eliminated, see what the alternator voltage does. If the surging is eliminated and the voltage is still out of regulation (assuming idle is 700 rpm or better), then I'd be considering putting the stock pulley back on the alt and see what that does.
Then, with those two items eliminated, if the regulator isn't regulating, then I'd be checking that connector plug on the back of the alt to be sure all is clean there.
With a faulty connection being eliminated...now you're down to the regulator itself. Time to pull that alternator and swap regulators (with a quality one this time) as re-builders don't always use "the good stuff".


Good luck my man!

P.

[WB9MCW]

Hadi my old speedboat would always start but it had this same surge thing at idle in the no wake zones -- I would notice it a night the most since the lights were on.

My mech. changed out the alt too and no fix -- he spent many hours on this one and it in the end turned out to be a multi-junction connector on the wire harness that had a bunch of corrosion on it and after a replacement of the mega connector all was well.

He never did figure it out it was the factory that actually came up with the idea to check that connector--

he only charged me $100 in the end since that was all the repair should have cost.

he told me that he had at least 100 hours in the investigation however -- good thing he is one of my neighbors and a good friend too!! lucky me on that one.

[HADI-ZR1]

Happy holiday my friends.:occasion1

update:
I bought new battery 56A.

i noticed that when the car at first start warm up, the charging needle show at 3/4 (900 RPM), then it goes to 1/2 @ 900 RPM. when engine is warm!
what is your conclusion?:hello:

[Paul Workman]

Happy holiday my friends.:occasion1

update:
I bought new battery 56A.

i noticed that when the car at first start warm up, the charging needle show at 3/4 (900 RPM), then it goes to 1/2 @ 900 RPM. when engine is warm!
what is your conclusion?:hello:

That is normal (w/o looking at your particular situation)

P.