Alternator test question

Is there a way to test an alternator while it is in the car? I always just popped them out and bench tested them at the local parts place.

 

i put a volt meter on them while the engine is running....should be around 13.5 to 14 volts

 

How do you do that? I think I see how, but tell me anyway.

 

I read that if the alt is charging, the back side will be magnetic. See if it draws a screw driver to stick to the center on the back

I read this in hot rod or some magazine, it may be worth a quick try - I have always been meaning to try it myself - i just never remember it when the motor is running

 

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How do you do that? I think I see how, but tell me anyway.

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put a volt meter on it....the black(-) to ground and the red (+) to the output(where the big wire is)of the alternator...this will tell you if it's charging

 

Another quick check is to remove the positive battery terminal while it's running. If it dies, the alternator is hooped!

 

Pull one of your battery cables. If the engine dies, the alternator isn't putting out. If the engine runs, the alternator is putting out. However, it may not be the correct voltage. Put a voltmeter across the battery - should read above 13.5 volts once the alternator kicks in (usually by 1500 rpm).

Screwdriver to the back does tell if the alternator is generating voltage, but not how much.

In general, if the screwdriver test OR the pull-the-battery-cable test are good, chances are it's fine.

Good Luck!

 

Most autoparts have a volt tester that you just lay on the wire while running and it picks up currernt flow. It will tell you what's going on. They are cheep. Also pulling a Batt. cable while running will often surge the alt. and cause a diod to blow. It's OK with a Gen but taboo on alt.
The Wizzard

 

Hmmm...I read a pretty cool post on this somewhere...

Hello, walls!!!


http://www.jalopyjournal.com/ubbthreads/showflat.php?Cat=&Board=UBB1&Number=277546&Forum=UBB1&Words=scary&Match=Entire%20Phrase&Searchpage=0&Limit=25&Old=allposts&Main=276825&Search=true#Post277546

 

You can lead a horse to drink Hack, but you can't make him water...

 

Never liked horses, Joe...ever since one "watered" on my shoe!

 

Plbtpblt! To the two of you.

I wanted an answer, not a tome to read through.

 

Put a volt meter on your battery with the car off.... it should read about 11 volts. Start the car and it should read about 14 volts. If it doesnt then pull the alternator and have it checked.

 

PetT..uh-uh !! a 12 volt battery SHOULD read 12.6 volts.... ( about 14 with motor runnin').....at 12 volts or below it is considered dead !!

Jersey Skip

 

Ha Ha Ha....and I thought I neatly labeled each set of paragraphs "Starting", "Charging", "Shit Don't Work", etc to make looking up info easier!!!

Sheeesh! Eye strain and cramped fingers for NOTHING!

 

i've seen plenty of alts with good volts and next to no amps. you need to check the amps also, but you need a carbon pile tester to do so. (vat 40)