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03-28-2013, 01:16 AM
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#1 |
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Registered User
Join Date: Feb 2013
Location: Fresno ca
Posts: 77
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Alternator question
I replaced my battery with an optima red top today and then I hooked up an multimeter and noticed that my alternator is pushing 12.11 volts at idle does that seem a little low?? What are normal numbers??
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03-28-2013, 01:26 AM
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#2 |
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Registered User
Join Date: Dec 2012
Location: Altoona Iowa
Posts: 481
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Re: Alternator question
not low at all......you dont want to see it drop charge below 11 and definitely never charging above 14......you will fry your battery and electronics in the truck.
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03-28-2013, 01:28 AM
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#3 | |
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Registered User
Join Date: Feb 2013
Location: Fresno ca
Posts: 77
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Re: Alternator question
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03-28-2013, 01:39 AM
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#4 |
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Registered User
Join Date: Dec 2012
Location: Altoona Iowa
Posts: 481
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Re: Alternator question
I would call 12 normal at idle........it will raise just a bit with higher rpm
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03-28-2013, 01:47 AM
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#5 |
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Registered User
Join Date: Feb 2013
Location: Fresno ca
Posts: 77
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Re: Alternator question
Thanks for the info bucks
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03-28-2013, 07:51 AM
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#6 |
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Registered User
Join Date: Aug 2009
Location: Alden NY
Posts: 2,705
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Re: Alternator question
Your alternator should put out 14.2 or 14.3 volts. Take it to a NAPA store and have it checked.
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1961 C1 Corvette 1959 El Camino 350 TPI, 9" 4 w disc 69 Blazer K5 - sold July '20 2021 Durango RT 5.7 |
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03-28-2013, 09:30 AM
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#7 |
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Registered User
Join Date: May 2012
Location: Central TX
Posts: 223
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Re: Alternator question
What alternator do you have? I believe some put only put out more current if you have your truck at 1000 RPM or higher.
Mine reads 12.4V when sitting but when it is running it jumps up to ~14.4V.
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'72 GMC Super Custom 1500 350 V8 w/AC |
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03-28-2013, 09:33 AM
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#8 |
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Registered User
Join Date: Oct 2005
Location: Overland Park, Ks.
Posts: 5,229
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Re: Alternator question
Unless the bat is not fully charged or you have a lot of acessories on you should charge at about 14 volts even at idle.
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03-28-2013, 10:40 AM
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#9 | |
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Registered User
Join Date: Aug 2009
Location: St. Paul MN.
Posts: 1,996
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Re: Alternator question
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Fuzzy |
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03-28-2013, 10:56 AM
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#10 |
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Registered User
 
Join Date: Dec 2012
Location: Chandler AZ
Posts: 1,149
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Re: Alternator question
there are a lot of variables.
Is EVERYTHING stock? If so you may not see charging until 700 rpm or so. You might want to rev it slightly to 1000 rpm and see if charging starts. Check connectors and grounds on the alternator, regulator and block. Make sure you don't have dirty or bad battery cables. With a DMM check the voltage at the post of the battery to ground and the cable end to ground. It should be the exact same. Check the belt to make sure it isn't glazed loose or frayed. that can cause slippage on the pulley and make it need higher RPM to see the charge. If all of that looks OK, then pull the alternator and have it tested. If it is bad and needs to be replaced, and you have an external regulator, you may wish to change the regulator at the same time.
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1970 Longhorn, Front Disc, 350/4 bolt, 882 heads, HEI, Edelbrock, 700R4, HO-52/4.11. 1996 Corvette, Collector Roadster, LT4, 396, 450RWHP, 6sp, 4.11/Dana44/posi 5 point roll bar And let us not grow weary of doing good, for in due season we will reap, if we do not give up. Gal 6:9 Last edited by Longhorn 70; 03-28-2013 at 11:05 AM. |
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