alternator or battery problem help
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From: southern california
alternator or battery problem help ok im a mechanic for trade but im kind of second guessing myself.
i have an 02 ss dumdumdumdum. here is what happened, i left my car to sit from monday to saturday with a radar detector plugged in. i did start it once ( barely) on wednesday to see if it had battery left . i should have unplugged the radar but forgot. i went to start it today (sat) and it was dead . so i jumped it and it fired right up , voltage was low so i figured it needed to charge more. so i drove home for a good 45 minutes when i noticed this and it was still at about 13.0 volts avg (12.7-13.2) so im thinking its the alt. so i take it home and let it set for a couple hours and it starts right up when i go back to it. i try starting it and pulling the cable from the battery and the car runs fine and when i checked it read (13.7-14.0) from being cold started . then proceed to take a drive as it read 13.8 and went down to about 13.5 on my aeroforce. i also load tested the battery( yellow top ) and it was fine
for electronics i have a viper alarm, aeroforce scan guage, and a a 500 watt sub amp.
i have these all in for some time with no probs until i let the car sit or i just never noticed.
i just dont want to replace the alt and it not be the prob.
any advice or experience?
i have an 02 ss dumdumdumdum. here is what happened, i left my car to sit from monday to saturday with a radar detector plugged in. i did start it once ( barely) on wednesday to see if it had battery left . i should have unplugged the radar but forgot. i went to start it today (sat) and it was dead . so i jumped it and it fired right up , voltage was low so i figured it needed to charge more. so i drove home for a good 45 minutes when i noticed this and it was still at about 13.0 volts avg (12.7-13.2) so im thinking its the alt. so i take it home and let it set for a couple hours and it starts right up when i go back to it. i try starting it and pulling the cable from the battery and the car runs fine and when i checked it read (13.7-14.0) from being cold started . then proceed to take a drive as it read 13.8 and went down to about 13.5 on my aeroforce. i also load tested the battery( yellow top ) and it was fine
for electronics i have a viper alarm, aeroforce scan guage, and a a 500 watt sub amp.
i have these all in for some time with no probs until i let the car sit or i just never noticed.
i just dont want to replace the alt and it not be the prob.
any advice or experience?
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From: Tomball/Nacogdoches TX
I am having almost an exact same problem with my car. It drives and performs fine but my voltage reads damn near 12 volts:
The car takes sits for a couple weeks at a time and I accidentally left the keys in the ignition overnight last week. Jumped the car and it fired just fine. Ever since the voltage has been pretty low.
The car takes sits for a couple weeks at a time and I accidentally left the keys in the ignition overnight last week. Jumped the car and it fired just fine. Ever since the voltage has been pretty low.
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From: Tomball/Nacogdoches TX
Furthermore, since I killed the battery, the gauges reset themselves when first cranked on two occasions. The needles just went to max and then back to norm
Last edited by Brian2006; May 18, 2008 at 09:47 PM.
When the battery is very low, it is showing a large resistance load to the charging circuit. Basically the low battery is needing a large ammount of current to just charge it up. So while this is still happening the voltage will drop.
Basically you have to figure out what is the wattage needed to charge the battery. With that relationship established, you can see that inorder to increase the amprage out, the voltage will drop. (W = V x A) (Example 100 W = 10V x 10A or 100 W = 12v x 8.333A or 100 W = 13V x 7.69A) Current is what is really needed to recharge the battery so while it's in a low state, the battery is going to demand more current which will cause voltage to drop.
Basically you have to figure out what is the wattage needed to charge the battery. With that relationship established, you can see that inorder to increase the amprage out, the voltage will drop. (W = V x A) (Example 100 W = 10V x 10A or 100 W = 12v x 8.333A or 100 W = 13V x 7.69A) Current is what is really needed to recharge the battery so while it's in a low state, the battery is going to demand more current which will cause voltage to drop.
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From: Massachusetts
Never trust your dash gauge in an absolute sense. You can somewhat trust it in "it usually read 13~14 but now it's reading 11~12" (relative sense) but you can't trust it as in "My gauge says 12V so my battery is 12V." You need a multimeter for that.
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x2, they aren't very accurate
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From: Tomball/Nacogdoches TX
When the battery is very low, it is showing a large resistance load to the charging circuit. Basically the low battery is needing a large ammount of current to just charge it up. So while this is still happening the voltage will drop.
Basically you have to figure out what is the wattage needed to charge the battery. With that relationship established, you can see that inorder to increase the amprage out, the voltage will drop. (W = V x A) (Example 100 W = 10V x 10A or 100 W = 12v x 8.333A or 100 W = 13V x 7.69A) Current is what is really needed to recharge the battery so while it's in a low state, the battery is going to demand more current which will cause voltage to drop.
Basically you have to figure out what is the wattage needed to charge the battery. With that relationship established, you can see that inorder to increase the amprage out, the voltage will drop. (W = V x A) (Example 100 W = 10V x 10A or 100 W = 12v x 8.333A or 100 W = 13V x 7.69A) Current is what is really needed to recharge the battery so while it's in a low state, the battery is going to demand more current which will cause voltage to drop.
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From: McChord AFB, WA
Sounds like a bad voltage regulator, and since it's attached to your alternator you will have to replace it. I just had the same thing happen to me this past weekend. My warenty covered it so the stealership replaced it and problem solved.