Do I need a new alternator???
Thread Starter
Melting Slicks
Joined: Jan 2003
Posts: 2,713
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From: Shreveport LA
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Do I need a new alternator???
Two (2) questions....One (1)...if my multi-meter reads 14.7 volts coming out of the alternator (red lead to the back of the alternator while the engine is running and the black lead to a good ground) and the battery reads 14.6 volts... do I need a new alternator?
And (2) will a 140 amp or 100 amp alternator hurt the battery or the wiring system?
The reason I'm asking is because I just got a brand new 770 CCA battery from Advance Auto. I connected a Battery Tender up to it and got the green light (after about 30 minutes of charging). After starting the car, and driving it for about 30-45 minutes and rehooking the Battery Tender when I got back, it takes about 3-4 hours before the battery is fully charged. So I'm wondering if the alternator is heading south....
Do I need to get a new one???
And (2) will a 140 amp or 100 amp alternator hurt the battery or the wiring system?
The reason I'm asking is because I just got a brand new 770 CCA battery from Advance Auto. I connected a Battery Tender up to it and got the green light (after about 30 minutes of charging). After starting the car, and driving it for about 30-45 minutes and rehooking the Battery Tender when I got back, it takes about 3-4 hours before the battery is fully charged. So I'm wondering if the alternator is heading south....
Do I need to get a new one???
Burning Brakes
Joined: Mar 2014
Posts: 904
Likes: 46
From: Crestline CA
I think all is good. 14.6v is plenty and length of time it takes for the battery tender to go solid green isnt really a good way to gauge charging system condition. If anything, get the battery load tested and if its good dont give it another thought.
No, a high amp alternator wont hurt anything except your pocketbook. But unless you have alot of add on electrical equipment(electric fans, big stereo, etc.) you probably dont need one.
No, a high amp alternator wont hurt anything except your pocketbook. But unless you have alot of add on electrical equipment(electric fans, big stereo, etc.) you probably dont need one.
Melting Slicks
Joined: May 2012
Posts: 2,192
Likes: 343
From: Allenton Wisconsin
13.6 to 14.2 VDC is factory spec on GM charging rates with the Delcotron alternator. Unless you have added any electrical accessories you don't need to up alternator output. Jegs has a kit to upgrade the Delcotron alt to 100 amp output for $40. Then you should increase the output wire size from the 12awg wire to at least a 8awg. T
Pro
Joined: Aug 2014
Posts: 508
Likes: 59
From: Oscoda Michigan
You can also find someone with a load tester like a VAT40 or MT522 that can put a load on your electrical system and read the output amps. If you have a failed diode in the alternator it can still show good voltage with a reduction in amps available. As has been noted the time to obtain a green light with a tender is not a sign of condition of either your battery or charging system. Mike
Le Mans Master
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From: Fernandina Beach FL
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Rather than guessing at a green light....
You might have 14.7 V DC BUT how much AC?
Here's how to tell if your diodes are in good shape-
With engine running about 2500RPM and headlights on- measure the AC voltage at the alt- output on one lead and the other lead on the alt's case.
Should be less than .5 volts AC.
A bad diode will drop 33% of Alt's output.
Richard
You might have 14.7 V DC BUT how much AC?
Here's how to tell if your diodes are in good shape-
With engine running about 2500RPM and headlights on- measure the AC voltage at the alt- output on one lead and the other lead on the alt's case.
Should be less than .5 volts AC.
A bad diode will drop 33% of Alt's output.
Richard
Drifting
Joined: Jul 2011
Posts: 1,825
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From: Boca Raton Florida
Two (2) questions....One (1)...if my multi-meter reads 14.7 volts coming out of the alternator (red lead to the back of the alternator while the engine is running and the black lead to a good ground) and the battery reads 14.6 volts... do I need a new alternator?
And (2) will a 140 amp or 100 amp alternator hurt the battery or the wiring system?
The reason I'm asking is because I just got a brand new 770 CCA battery from Advance Auto. I connected a Battery Tender up to it and got the green light (after about 30 minutes of charging). After starting the car, and driving it for about 30-45 minutes and rehooking the Battery Tender when I got back, it takes about 3-4 hours before the battery is fully charged. So I'm wondering if the alternator is heading south....
Do I need to get a new one???
And (2) will a 140 amp or 100 amp alternator hurt the battery or the wiring system?
The reason I'm asking is because I just got a brand new 770 CCA battery from Advance Auto. I connected a Battery Tender up to it and got the green light (after about 30 minutes of charging). After starting the car, and driving it for about 30-45 minutes and rehooking the Battery Tender when I got back, it takes about 3-4 hours before the battery is fully charged. So I'm wondering if the alternator is heading south....
Do I need to get a new one???
2-No, 140m AMP alt is designed for our cars and it will do no harm to it. Because it is triple regulated, it only puts out what the electrical system is demanding, nothing more. Our OEM alts after a while (they get old and tired) and not provide enough amps at stop lights but your numbers are good. So too many ted lights, you are draining your battery instead of charging it.
3-Yes that is also normal for your charger to take 2-3 hours because if it is CTEK, it is running some tests first to see where the battery is.Because it is good, you get green in 3 hours. If your battery was really low, it would even take overnight of charging to get to green.
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Drifting
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From: Boca Raton Florida
Originally Posted by HeadsU.P.
Note the dates, gsflyer2011
Is my vette stock?? HAHA
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