Charging system Problem !

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??!
where is the problem you think guys?
GUess why i post this thread in Parts wanted??









I WAS SMOKING! , 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.


Tom

[gbrtng]

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

[WB9MCW]

Originally Posted by gbrtng

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.

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...

[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]

Originally Posted by gbrtng

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!!!

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 !!
Took this picture just now before starting my car! its 2:00 AM , and still snow on him!:-)

[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.