monitor charging voltage

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  #1  
Old 02-04-02, 09:17 AM
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monitor charging voltage

Hello I would like to monitor the charging voltage from inside the car while driving with a digtial fluke meter.I dont want to run a long wire to the battery posts can I just make up something wereI can plug it into the cig lighter?
 
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  #2  
Old 02-04-02, 09:29 AM
mooser1
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absolutely.....any auto parts store will stock a "cig lighter" adaptor plug you can attach to your fluke wiring........Radio Shack also carries these plugs.......JC Whitney sells gauges for this exact purpose if you don't feel like wiring up a plug......
 
  #3  
Old 02-04-02, 09:30 AM
Joe_F
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Radio shack probably has something you can use, but why? .

Do the charging system test I tell everyone to do:

Charge the battery. Measure it with the fluke, should be 12.5 volts.

Now, run the engine, no accessories on. Should be around 14.2 volts.

Add accessories one at a time, such as wipers, defroster, headlights, turn signals/flashers, A/C, etc.

If the alternator doesn't put out 13.5 volts or more, it is likely wiped.

Try that and tell us what you find.
 
  #4  
Old 02-04-02, 10:05 AM
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reason why I want to do it

The reason I want to do it is because I belive the alt is over charging due to bad diodes the light goes on and off on the dash and I want to see when it goes on and off (what the alt is doing during this time) if the battery is full the alt should not charge it and i think it might be.I checked it and it is charging the battery with no light on but when the light goes on I am just not fast enough to get out and put the leads on the posts by that time the light is off again.I dont want to overcharge the battery again.
The light will go off if I rev the engine.
It will also stay off for as many as 25 miles and then it starts going on.
 
  #5  
Old 02-04-02, 10:35 AM
Joe_F
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Still, it should come on at idle with all the accessories on because:

1) You have the greatest load on the alternator at that time.
2) It is turning slower.
3) Due to #2, it is putting out less.

If it's weak, it's going to be evident at idle with all the goodies on .
 
  #6  
Old 02-04-02, 11:06 AM
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comes and gos when it wants

it does not seem to matter if the engine is at idle or hwy speed load or no load it comes and goes when it wants,
sometimes it will stay on for only a few seconds and go off and other times it stays on till I rev it up by bumping the gas petal.I have put a full load on it lights,heater,rear window defrost etc. it shows charge.what should it read when the battery is full? the alt should not charge right?should be about the same as battery voltage I would think.
I have always thought the battery is there to suplement the alternator it acts as a storage and all the alt does is replace the lost power then shuts off again.
 
  #7  
Old 02-04-02, 02:32 PM
Joe_F
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Do my little test.

Tell me what you find .

That's a pretty decent test of load output.

How's the condition of the drive belt? Might be slipping at times and causing a discharge. If it's over 4 years old, pitch it for a new one without question.
 
  #8  
Old 02-10-02, 12:56 PM
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still have light joe im going to blow up car

Hello again all I am totally frustrated now I am still having the problem with the battery light.Here is the test I have done as per Joe first let me say I did get another Alt made by Delco and a new belt.so 5 alts later two batterys and a drive belt im still in the same boat.But I am able to replace the alternator in record time less then 5 min.
Battery voltage engine off with fluke is 12.57V
start at idle no load 14.38v
lights on 14.37v
lights with high beam 14.33v
heater blower motaor on high with all the above 14.31v
brake lights and all the above 14.27v
then the engine cooling fan came on and it dropped to 13.1v
when the battey light is on voltage is 14.13v
when it is off it is 14.05v
I am starting to suspect a battery cable but the car starts strong.
what else could it be please help I am in the market for some explosives now
 
  #9  
Old 02-10-02, 01:08 PM
mooser1
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sounds like the charging system is right on.....I would suspect the idiot light circuit itself as having a short.....if it were mine I would unplug your "battery" light and install an aftermarket amp gauge in the car so you will always get a true reading of alt. output....if you wish to keep everything "stock", find a manual or use the Chilton's site on Joe's signature info to get a wiring diagram and trace out the dash light circuit.......this can get complicated.....
 
  #10  
Old 02-10-02, 01:53 PM
trendar
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Yeah, seems like something awry in your warning light system- especially since you've gone through 5 (!?) alternators and still have the problem-
Try to make sure all your secondary grounds are clean and tight, too. Maybe a wiggle/jiggle routine at the harness while someone watches for the light.


the alt should not charge right?should be about the same as battery voltage I would think.
I have always thought the battery is there to suplement the alternator it acts as a storage and all the alt does is replace the lost power then shuts off again.
The alternator is actually supplying current all the time when you run the car, but it just varies the amount as necessary to maintain the regulated voltage; the battery is acting like a reservoir to stabilize things and supplies extra current when needed (and on startup, when the alternator isn't running).
 
  #11  
Old 02-10-02, 04:52 PM
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checking grounds is next

Thanks for the input I will start checking grounds as soon as I find them all.There are so many wires and hoses in the buick I dont know were to start.My main concern is that my wife will get stranded because of a dead battery caused by overcharge condition or it might even blow up causing a real mess with battery acid all over the place.Does anyone know what the voltage should be at the battery posts with the battery fully charged no load?I was thinking about 12.6 volts.if it is that I have never seen it.
What all is involved with installing an amp guage in a late model 96 buick I have done it before a long time ago on a 65 dodge but those were the simple days.I still want to blow up the Buick and that way the only ground I need to seek out is were to bury it
 
  #12  
Old 02-10-02, 05:01 PM
mooser1
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according to Joe's info, battery should read 12.5 amps no load, sounds like you are ok there......aftermarket gauge is simple to hook up, detailed instructions included with the kit from your local auto parts.....
 
  #13  
Old 02-10-02, 05:27 PM
Gix
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had a similar problem on a customers car , intermittent batt light coming on even though charging system was operating corectly , started wigling conections , grounds powers , whatever i could get my hands on , to try and reproduce the fault in the shop , eventually found a bad fuseible link at the starter motor, this was a 94 olds ninety eight, may want to have quick look in that area , you may get lucky
 
  #14  
Old 02-10-02, 05:43 PM
mooser1
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this is a good suggestion.....to check a fusible link, grasp it at both ends and gently try to pull it apart....if it feels solid, it probably is, if it "stretches" it's probably junk.....good luck
 
  #15  
Old 02-10-02, 06:01 PM
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fuseable link how many are there

I know of only one fusable link and it is paralel to the battery cable near the battery is this the only one?I have heard that if this link is shot the car will die and get NO power at all.but I will wiggle and pull on it I am at a point I will try anything including the blow up the problem method.
 
  #16  
Old 02-10-02, 06:37 PM
mooser1
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I honestly don't know if this is the only one or not, Joe would probably know, he owns some of this iron.....I did like your suggestion about the dynamite but must warn you, the electronics on newer ones are even more of a PITA, trust me.......
 
  #17  
Old 02-10-02, 06:54 PM
Joe_F
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These folks are right on. Check for a short at the wires or a poor ground/dirty terminal.

Get a wiring diagram and go from there.
 
  #18  
Old 02-10-02, 07:21 PM
trendar
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Check the voltage at the battery terminals after you've been driving a while to see what it reads; if it's at or below what your readings were in your prior post, I wouldn't really worry about it much. Out of curiousity, you might try reading the AC voltage using your dmm to see if you have AC ripple on it. Shouldn't see much on it.
 
  #19  
Old 02-11-02, 09:29 AM
Joe_F
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Also, most automotive scanners have a voltmeter function. They will plug into the lighter and underneath at the diagnostic connector.

You can then drive around until your heart's content and measure voltage.
 
  #20  
Old 02-16-02, 11:38 PM
trendar
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Re: checking grounds is next

Originally posted by michael van
What all is involved with installing an amp guage in a late model 96 buick I have done it before a long time ago on a 65 dodge but those were the simple days.
A voltmeter is far easier to install and would give you better information on how the charging system is working, so I would put one of those in if you have to. If you check the voltage at the time you get the warning light under the various load conditions, and it is within range, I wouldn't be too concerned about the battery blowing up. If you read 15V or some such nonsense, then I'd worry-
 
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