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the voltage regulator is probably built into your alternator already.
if the alternator puts out over 12.5 volts above idle, it's fine.

so i should i buy a voltage regular to adjust the voltage? i was always under the impression that i should not be doing 12.4.

yes, the alternator produces AC voltage, and the regulator (external or internal) rectifies that to DC voltage and adjusts the level, but above idle the voltage increases to a charging voltage, which is >12.5VDC, which was what I was conveying.
Peak current output is what drops as the alternator warms up, which is why they all hae a hot and cold rating, and ideally, you want to use the hot rating when choosing an alternator to match your needs.

The alternator isn't really off per se at idle, but it's not at full output, and voltage isn't at a charging level to produce the forward bias for battery charging at idle because it would put more drag on the motor sitting at stopights or in traffic, and that generates heat. Now if you do have an external variable voltage regulator you can set idle voltage as well and circumvent that low idle voltage but most newer cars have internal regulators unfortunately.

Good point though.

KikiTheCat wrote:yup at idle the alternator free spins to reduce load on the motor rotating assembly and reduce drag and loss of power, and reduce things like torque on your starter.
above idle the alternator is at full speed from the belt drive, and puts out both more current and a higher voltage.

"higher voltage" is up to the voltage regulator... which typically, as the alt heats up... the voltage will actually go down and then level off.

once the alt gets going, it should pop up to its operating voltage... and as you increase RPM's current potential should be increased until it finally tops off.

Let it also be known that you don't want the alt to be completely OFF at idle... which it seems is the case here. You may have to increase your idle so that your car doesnt die if you sit at a stop light too long with the system going.

yup at idle the alternator free spins to reduce load on the motor rotating assembly and reduce drag and loss of power, and reduce things like torque on your starter.
above idle the alternator is at full speed from the belt drive, and puts out both more current and a higher voltage.

Most...almost all alternators dont start raising voltage until about 2000-2500 rpm. So unless you notice your lights dimming all the time...i wouldnt really worry about it.

TEDD

Most HO alts are designed to unload above engine idle. They also have a tendency to run at about 13 volts too. This is just from what I have read. Before mine died, it ran and was designed to put out 14.4.

i got a HO alternator about 1 month ago, i got it installed and did the big 3, one question, the reason a person gets a HO alternator is to keep the voltage up right? well my car does around 12.6 most of the time(idle of on street) so when my music is on im like at 11.5, as soon as i step on the gas it goes to 14, but then it falls quickly, so my question is did i do something wrong or should i just put the stock one back in and be at 14.2 idle like i used to be?