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I think the volts when you are at a light sound low, I will go to 11.8 at a light but not that low. I don't know for sure but that load on your alternator might eventually damage it. At some point you will have your heater, head lights and wipers on and make matters worse. You are drawing more than it can provide at 625 RPM. I think the stock unit is 140 amps, someone here installed a 200 amp alt, you might want to check into that..

That said, have your battery checked and clean your battery connections

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I agree the volts when stopped seem low. Even 12.9 volts seem a bit lower than average. Most see volts at least in the low 13s during normal driving. I often see volts range into the mid to high 13s to 14 – 14.2. In the morning volts will go as high as 14.5. Have you seen the SYSTEM VOLTAGE error message on the DIC. I’ve seen voltage only on rare occasion drop to about 11.8; however, it does not stay there long even at idle, as the alternator/voltage regulator will adjust to the heavy load and push voltage into at least the low 12s and often higher. For example, during the winter when stopped at a traffic light with the heat, lights, and radio on, voltage may drop briefly after initial stop. After a brief moment the voltage regulator compensates for the heavy load because voltage increases even without stepping on the gas to raise rpms. If you’re experiencing low voltage readings on a regular basis without the voltage regulator compensating, I would at least clean the battery cables as BodybyFisher suggested. This may not help but it’s a good place to start.

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I agree, those are low.....

How long since you bought a battery???

As BbF and MAC suggest, check your connections, and get the battery load tested... lots of parts places do that for free....

To make a long story short, bad batteries have caused me a lot of strange problems, and new batteries have solved a lot of problems....

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None of your car audio cronies will agree with me but you need to get rid of the "power cap" first before you do anything else. If you have to have it in there for looks and it has a voltage readout on it - find a way to power the display without the capacitor being in the system.

All the capacitor is made to do is provide short bursts of power when a heavy bass note hits. With most songs normal people listen to, there is alot of bass all of the time, the capacitor helps for the first three seconds and then it is constantly trying to recharge itself and in doing so it becomes just one more load on the charging system.

Believe it or not- the "power cap" is just an extra load on the system.

Secondly, buy a smaller battery. Larger batteries are the same as the cap in that they will constantly be trying to recharge themselves and larger batteries are more of a load on the system. The only reason to have large batteries is for extended motor off playing time. If you listen to it alot without the motor running- you do need the large battery.

Thirdly- Alternator Alternator Alternator- that is what is important when you've got a high current draw stereo system. Alot of idiots will try to con you into certain tricks and stupid 7777 to make more power come out of the alternator. A popular one is to put a smaller pulley on there so it spins at a higher rpm. That's good at idle because it supposedly is turning alot faster and you can get peak output at idle- I don't know for sure but it probably tears the alt. to hell.

I don't know what rewinding the alt does. I think it is another cute trick,

A good shop can build you a quality 200+A alternator for under $300 with custom brackets.

The next thing to consider is how effecient your amplifiers are. If you have inexpensive aplifier equipment- it is probably ineffecient and that means it needs more juice. My ex wife had a Lanzar 1200D mono block amplifier. It put out a good clean 1200W but it brought a 140A alt to its knees. On the other hand I tried a 1500W rockford amp and it was fine with the stock 90A alt.

Also remember that when anything is underpowered you could blow your speakers. More subwoofers are blown to hell because of a dirty underpowered signal than are lost to overdriving.


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