Startin alternator?

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  #1  
Old 02-17-13, 08:21 AM
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Startin alternator?

Hi folks.
y'all know, I am dumm electrically. Came across this guide today:

Turn off the car and test the battery with a voltmeter. Place the red end of the voltmeter to the red battery terminal and the black contact to the black terminal, avoiding touching your skin to the battery. If the battery reads above 12.2 volts, it has enough juice to start the alternator, which can then be tested with the voltmeter; if not, either get the battery charged and re-test or try one of the methods below.

The battery is needed to start the alternator, which, in turn, keeps the battery charged. This means that if your battery is low, it will be unable to get the alternator going, rendering any additional voltmeter-testing totally useless.


What am I missing here? Always thought, battery starts engine by applying power to STARTER, and ENGINE in its turn keeps alternator running, and THEN alternator is charging battery back.
That's WikiHow. What am I missing?
 
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Old 02-17-13, 08:27 AM
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Unless you are running a Kohler starter/generator on a lawn tractor, the battery starts the engine via the starter, which turns the belts to energize the alternator which returns voltage to the battery. You are right. Is this a quoted link?
Sounds a little like it was written at a quilting party rather than by an auto mechanic.
 
  #3  
Old 02-17-13, 08:54 AM
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Well......you do need voltage to the alternator (exciter voltage?) for it to produce an output. Once the engine is running, that voltage is produced by the alternator itself. Thats why on older cars, once it was started, you could drive with the battery disconnected. Newer cars, that can fry the electronics since the battery is not there to help "regulate" the voltage.

That's also why on older cars, you could unplug the small connection on the alternator and hold a screwdriver against the end to test it. If it was plugged in and the screwdriver stuck to the end, the alternator was "probably" working. Unplugged, no exciter voltage, no magnetism produced, no output, no stick. Plugged in and the screwdriver doesn't stick....you have a problem. Whether that works with new cars...I dunno. Some new cars also use the alternator as a booster motor.
 
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Old 02-17-13, 09:05 AM
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Ukrbyk,

The problem here is that you are confusing the function of an alternator with the starting of an engine. For starting an alternator is not necessary. Donít believe me????

Then remove the alternator from your car and try starting it. The car will start and run off the charge in the battery until the battery dies. When the battery dies, take another fully charged battery, install it and start your engine. Moral of the story is, that as long as you have a supply of fully charged batteries you donít need an alternator. Not a practical idea though. Visit the website below to see why alternators are necessary.

HOW DOES AN ALTERNATOR WORK?

Thank You
Amy
 

Last edited by the_tow_guy; 02-17-13 at 12:30 PM. Reason: Fixed formatting
  #5  
Old 02-17-13, 09:10 AM
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Is the "guide" for an old Hyundai?
I'm a retired electronics tech and some of the 70's and 80's manuals for Korean and Chinese products were laughable. Google translations do a better job than they did.
 
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Old 02-17-13, 09:37 AM
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Have no idea why I am chastised for this. Told you, it's wikiHow. I was looking something up for some lost soul at a different forum, that keeps swapping batteries on his Cherokee like every year or so. Came across this BS.

2 Ways to Check an Alternator - wikiHow
 
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Old 02-17-13, 09:40 AM
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Amy, I actually DROVE a car for about 15 minutes, slow pace, on battery only. Russian Morskvitch, back in g'ol times. Those were humongous batteries, for some reason called 75s, we usually bought them from sodiers for few rubles. They lasted about 2 years and didn't like warm weather. But I drove on one, and made it home. Don't remember, what exactly happened to alternator, but that was the case.
 
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Old 02-17-13, 02:30 PM
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Believe me, Amy fix 62, Igor knows his way around cars He was quoting a link that was totally off base. Thus my comments in post #2.
 
  #9  
Old 02-18-13, 06:21 AM
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The post should have said "excite the alt" instead of start the alt. This would have avoided all the confusion. I recently jumped a car with a totally dead batt. and when I took the jumpers off it died. Had to leave jumpers on for a minute till the alt got "excited". They need electricity to create electricity.
 
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