voltage in car fluctuating up and down

[nightcat]

ok her e is the deal, i chnaged the alt, and did the fix, plus upgraded wires and i also changed the three wire harness to a new one. i dont have a voltage guage as yet so im using the one that came on my pioneer radio just to gove me an idea of whats going on when im driving. When i first start the car up it reads a little above 13 volts and sometimes 12.5. when im driving it and hit the brakes, it drops into the 11's and then rise back up above 12 real quick. it does the same when i role the windows up or down or even when i turn the heat or ac on. Does anyone have any idea on whats going?

thanks

[ThdrCat]

Hey you really can't go off that all that much. You have to realize that your radio is pulling voltage and it's reading the voltage to the radio not off the electrical system. Take a voltage meter to the battery and check.

[fade2blk]

yes electrnics require voltage, but what is going on.. once the windows switch has been pressed the motor requires current if it is not sufficient enought the voltage will drop. same goes with the brakes and other electrical components in the car.

you have stated that all the wiring was upgraded, how about grounds or the negative side was that upgraded as well?

[seaneyo99]

yes electrnics require voltage, but what is going on.. once the windows switch has been pressed the motor requires current if it is not sufficient enought the voltage will drop. same goes with the brakes and other electrical components in the car.

you have stated that all the wiring was upgraded, how about grounds or the negative side was that upgraded as well?

Reguardless if the voltage is high enough..... it requries more to start up any type of eletrical motor in this case the window motors. So there will be a slight drop in voltage as you first press the window button. firing up anything like that will at first put a strain on the elec. system. then the alt. will bring the battery back to full charge then inturn raise the voltage back to normal.