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Checking alternator in truck?

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BlueLite

05-11-2004 18:46:28




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I'm off subject here folks, but I just got a dead, or almost dead battery in my truck. Can't tell how old the battery is. It has idiot lights(I hate idiot lights) and none comes on while driving which means the charging circuit is supposed to be OK., Right? it comes on of course when you turn the ignition key when starting which is normal, then goes off when it's running.

Since I don't trust the dash light, can I start the truck then remove the battery. Then the distributer should run off the alternator if it's working right?

Don't know much about this stuff but any help would be appreciated.

Thanks.

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Mark W.

05-13-2004 09:53:25




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 Re: Checking alternator in truck? in reply to BlueLite, 05-11-2004 18:46:28  
BlueLite:

You're right to be suspicious of the instrument panel light. I've seen vehicles with dead alternators that pass the power-on dashboard lamp test but do not illuminate the alternator warning light when the engine is running.

As other respondents have suggested, the best check is probably with a voltmeter (about $10 - $15 at Radio Shack).

Mark W.



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Bob M

05-11-2004 19:06:19




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 Re: Checking alternator in truck? in reply to BlueLite, 05-11-2004 18:46:28  
First off if you have an alternator don't, don't, **DON'T** remove the battery with the engine running!! Even if your truck doesn't have electrical problems now, guarantee it will after you attempt this!

Regarding your charging problems, as you note the idiot light is next to worthless. About all it tells you is the alternator is spinning (ie. the belt's not broke), and the alternator is developing a voltage very slightly above battery voltage.

What you need is an accurate voltmeter placed across the battery. If the alternator is good the voltmeter will show 14.0 - 14.5 volts or so with the engine running. Anything less means the alternators has problems.

Don't have a voltmeter? Easiest solution is to remove the alternator and take it to Advance Auto, NAPA, etc. They'll test it for you for free.

Hope this helps...

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Bus Driver

05-12-2004 04:20:09




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 Re: Re: Checking alternator in truck? in reply to Bob M, 05-11-2004 19:06:19  
Locally, the Advance Stores test the alternator on the vehicle. Just drive over to the store. I also have been "preaching" for years about the potential damage of removing battery cables on a vehicle while it is running. The uncontrolled open causes the output voltage to rise enough to ruin diodes.



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Allan

05-11-2004 19:26:54




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 Re: Re: Checking alternator in truck? in reply to Bob M, 05-11-2004 19:06:19  
Hey Buddy Bob!!!

I'm certainly not going to argue with you on this subject this time around 'cause I found out today how really dumb I am. LOL!!

Just thought I'd throw that in. )grin(

BlueLite,

I'd do like Bob says and go have it checked with a simple voltmeter.

Allan



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james williams

05-11-2004 19:05:16




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 Re: Checking alternator in truck? in reply to BlueLite, 05-11-2004 18:46:28  
Reguardless what others say never remove battery cables while the motor is running,your system needs a Pos and Neg and when this is lost electricty tries to take the least reisistance,which could caues a melt down.There are other ways of checking a charging systen,and guess work is usally the most expensive



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onlytony

05-13-2004 15:54:36




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 Re: Re: Checking alternator in truck? in reply to james williams, 05-11-2004 19:05:16  
The other replies are correct about a good auto
parts store will test an alternator for free. The first thing I always check, with the motor off, see if you can turn the alternator with your
thumb or hand, because if you can the belt is going to be loose. If the belt is loose then the
alternator will not charge very well. For a fast test, with the motor running put a screwdriver behind the alternator and if it seems
like the alternator is acting like a magnet pulling the screwdriver to it, then the alternator
is probably going to be good.

About the battery, if it is bad I would recomend
against a Walmart brand. I have not had good luck
with them and the people I know that work there
say that those batterys should say Sam's Choice
on them.

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