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Old 08-29-2010, 10:48 PM   #1
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Default severe voltage drops

what would cause the voltage to drop from 13.1 to 11.5 to 11.8 when i am driving at night and i have my headlights on well i let off gas pedal and my lights get real dim and my voltage dropps severly like almost to 10 volts and during daytime my voltage stays at 12.1 mabye a little less is alternator the problem or could it be battery??????? please help these dee tee dee up here at autozone say everything is fine i say they are crazy thanx in advance
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Old 08-29-2010, 10:51 PM   #2
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could be alt or battery... if the battery can't actually retain a charge, then it will drop voltage any time the alt alone can't keep up with the electrical draw. if the alt is weak(and it sounds like it) then you could also see this kind of problem.
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Old 08-29-2010, 10:58 PM   #3
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Old 08-29-2010, 11:04 PM   #4
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ok thanx fellas ill get back to ya on that tomorrow i appreciate it
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Old 08-30-2010, 08:45 AM   #5
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If it'* dropping at a stoplight or when the rpm is under 650, that is understandable as the alt kicks off at about 650. (not positive on the rpm for your year, but it'* in that area).
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Old 08-30-2010, 08:48 AM   #6
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Might be worthy to take a look at your audio system and ensure it'* not drawing a high load.
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Old 08-30-2010, 07:58 PM   #7
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i think it might be my audio system draining my batt too much and my alt cant catch up with it what could i do to fix that prob ????? better batt and bigger alt mabye capacitor just a few ideas....... i have a 12 inch alpine type r with infinity refrence 611a amp and a 10 inch type r with a mtx jackhammer jh 600 amp on he 10 with stock batt and alternator
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Old 08-30-2010, 08:04 PM   #8
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a capacitor will not crutch an insufficent charging system, which is what you have if you plan on continuously running that sound system.

what you need is two-fold at a minimum: higher amperage alt and potentially a higher capacity battery.

capacitors charge and discharge more or less instantaneously, so whenever your amp drew any power, the alt would still have to replace it since capacitors don't have a lot of capacity compared to a regular auto battery.
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Old 10-19-2010, 11:37 PM   #9
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Engine at 1000 rpm the alternator should maintain 14.4 volts with headlights on. If you have additional current draws like an audio system, 13.6v is ok if you can live with occasional dim lights when stopped.

Alternators have 3 phase AC and the regulators have 3 sets of diodes. Very few cars can detect when 1 set of diodes goes out. But it will show up in the voltage measurements...i.e. the 14.4 volts isn't reached.

When faced with high current audio or other systems, change the alternator to a high current type...they are available for all cars. This will cure any dim headlight situation.
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