Suspicious voltage drop...



Suspicious voltage drop...

Postby DorianL » November 17th, 2014, 10:39 am

What do you guys think? My alt is a 55Amp Bosch. At idle I get 13.6 V

If I turns the headlights on, the voltage drops to 12.6 V

Something tells me that's prob not normal.

Correct?
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Re: Suspicious voltage drop...

Postby 87vette81big » November 17th, 2014, 11:25 am

DorianL wrote:What do you guys think? My alt is a 55Amp Bosch. At idle I get 13.6 V

If I turns the headlights on, the voltage drops to 12.6 V

Something tells me that's prob not normal.
Correct?

Test again at 2,000 Rpms on the dash tachometer Dorian .
Small Bosch alternators don't put out much current at idle.
Its a Toy compared to the CS144 I built for you on the TT.
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Re: Suspicious voltage drop...

Postby DorianL » November 17th, 2014, 11:29 am

87vette81big wrote:
DorianL wrote:What do you guys think? My alt is a 55Amp Bosch. At idle I get 13.6 V

If I turns the headlights on, the voltage drops to 12.6 V

Something tells me that's prob not normal.
Correct?

Test again at 2,000 Rpms on the dash tachometer Dorian .
Small Bosch alternators don't put out much current at idle.
Its a Toy compared to the CS144 I built for you on the TT.


Will do - that makes sense... Makes a LOT of sense.
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Re: Suspicious voltage drop...

Postby philly » November 17th, 2014, 6:18 pm

yep low revs that alternator is barely turning... for everyones information if you have a car that you only start once a month to "charge the battery" and let it idle in the driveway... it can take 30-45 minutes once a month of idling with no auxillary current draw for a stock sized alternator to restore the lost power from time sitting and the actual starting process you just put it through. guys who have very short (under 5 minute) drives to work have more frequent battery problems because they dont get enough recharge time throughout their use. just a little fyi
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Re: Suspicious voltage drop...

Postby DorianL » November 18th, 2014, 3:27 am

philly wrote:yep low revs that alternator is barely turning... for everyones information if you have a car that you only start once a month to "charge the battery" and let it idle in the driveway... it can take 30-45 minutes once a month of idling with no auxillary current draw for a stock sized alternator to restore the lost power from time sitting and the actual starting process you just put it through. guys who have very short (under 5 minute) drives to work have more frequent battery problems because they dont get enough recharge time throughout their use. just a little fyi


Yes, I am having those issues, already with the Ghia. I only drive it on weekends (crappy weather) and starting is becoming tough. I think one of the issues is that the Ghia is constantly searching for the key even when it's garaged.

Hmm, I'm going to see if I can find a way to get a permanent source of electricity in my garage and set up a trickle charge. For moment I have to extension cable juice over...
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Re: Suspicious voltage drop...

Postby 87vette81big » November 18th, 2014, 7:13 am

My old 1963 Pontiac Grand Prix is still together and running with 403 Olds Power & Turbo 400 Trans.
That car is basic as it gets.
The Delco 12 SI I built for it years ago draws just 1 milliamp Reverse diode bias current.
The car can sit 6-12 months.
Fires righr up every single time within 5-seconds.
Why I lke basic & simple.
Take the electronics out. Just a radio needed.
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Re: Suspicious voltage drop...

Postby Indycars » November 18th, 2014, 9:06 am

DorianL wrote:Yes, I am having those issues, already with the Ghia. I only drive it on weekends (crappy weather) and starting is becoming tough. I think one of the issues is that the Ghia is constantly searching for the key even when it's garaged.

Hmm, I'm going to see if I can find a way to get a permanent source of electricity in my garage and set up a trickle charge. For moment I have to extension cable juice over...


It probably won't change anything, but before jumping to conclusions, why not
measure the current draw on the battery when everything is turned off. It's so
easy to do, shouldn't take more than 10 minutes. It would help next time you
encounter this problem to know what kind of drain is Ok and what is not.

Maybe you have a short somewhere and current draw is higher than it should be.

If you have the battery specs, you should be able to calculate how long the
battery will last to get an idea how if the battery is holding up like it should.

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Re: Suspicious voltage drop...

Postby DorianL » November 18th, 2014, 11:03 am

Indycars wrote:
DorianL wrote:Yes, I am having those issues, already with the Ghia. I only drive it on weekends (crappy weather) and starting is becoming tough. I think one of the issues is that the Ghia is constantly searching for the key even when it's garaged.

Hmm, I'm going to see if I can find a way to get a permanent source of electricity in my garage and set up a trickle charge. For moment I have to extension cable juice over...


It probably won't change anything, but before jumping to conclusions, why not
measure the current draw on the battery when everything is turned off. It's so
easy to do, shouldn't take more than 10 minutes. It would help next time you
encounter this problem to know what kind of drain is Ok and what is not.

Maybe you have a short somewhere and current draw is higher than it should be.

If you have the battery specs, you should be able to calculate how long the
battery will last to get an idea how if the battery is holding up like it should.




Golden. I wonder how many Amps my DMM can take...
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Re: Suspicious voltage drop...

Postby Indycars » November 18th, 2014, 1:00 pm


Most can handle one amp, but the later ones can take 10 amps. The problem is
you don't know for sure what you need until it's too late. There should be a fuse
to protect the meter, so the worst you should have to do is replace the fuse ......
THAT IS THEORETICALLY ??? If you don't have a problem other than it's not charging
enough, then it should exceed 1/2 an amp at the most and likely something much less.

You could put a resistor in series with the meter to start out with. Might give you
some kind of idea what you are dealing with.

This is the meter I have, you can see there are two setups to measure current, but
ONLY one way should be used at first until you know how much current you are dealing
with. It's the only time I put the red lead in the left jack.

Innova_D3320.jpg



I'm sure you already were aware of the above, but some may not if they read
this thread.


You do not have the required permissions to view the files attached to this post.
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Re: Suspicious voltage drop...

Postby DorianL » November 30th, 2014, 10:19 am

Interesting. The plot thickens.

On the ghia my battery is typically flat after one week of not driving. I thought that was quick but who knows, maybe it's the keyless entry draw.

Well I measured that, the draw at rest, everything off except clock and keyless entry is: 0.08 Amps.
If I turn the headlights on, the draw is 3.5 Amps.

I swapped out my optima bad out in a regular batt. At idle hot, it was 13.89 volts. Idle hot with lights on, 13.67 volts. Raising rpm to 2-3000 had no effect on the voltage.

Hmm my guess is the Optima red top has come to the end of its long, distinguished career. I'll have to check when I bought it, but I think it's 7-8 years old.
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Re: Suspicious voltage drop...

Postby DorianL » November 30th, 2014, 11:39 am

Ummm. The batt is 10 years old.
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Re: Suspicious voltage drop...

Postby grumpyvette » November 30th, 2014, 1:25 pm

DorianL wrote:Ummm. The batt is 10 years old.


you did good the last one of those I bought lasted less than 5 years (Optima red top) but it was in a generator that only got used intermitantly
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: Suspicious voltage drop...

Postby DorianL » December 1st, 2014, 2:55 am

Yeah!!! There were probably other issues that I had with Chevy by never really noticed. :D

What surprises me is that the battery's last leg has an effect on charging voltage: if I turn headlights on, the voltage drops from 13.6 to 12.6, iirc.
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Re: Suspicious voltage drop...

Postby grumpyvette » December 1st, 2014, 9:09 am

If your multi- meter shows less than 13.7 volts while the engines held at 1200rpm,that tends to make me think the alternators rather worn or the voltage regulators shot! or the battery's defective and youll need to test carefully to determine the cause. once the engine reaches about 1200rpm you should see a rather constant 13.7-14.8 volts even with a rather depleted but functional, battery.
I can assure you that swapping from a 110 amp alternator to a 200 amp alternator on my 1985 corvette made a huge difference in the way the car runs and the strength of the ignition spark



viewtopic.php?f=48&t=10003&p=43220&hilit=test+alternator#p43220

viewtopic.php?f=36&t=3222&p=8575#p8575

viewtopic.php?f=36&t=1169&p=2392&hilit=test+alternator#p2392

viewtopic.php?f=70&t=986&p=2671&hilit=test+alternator#p2671

viewtopic.php?f=44&t=808&p=2957&hilit=test+alternator#p2957

viewtopic.php?f=36&t=63&p=5446&hilit=test+alternator#p5446

http://alternatorparts.com/cs-144-special-offer.html

http://www.summitracing.com/search?Sort ... alternator
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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