I have a friend with a voltmeter built in to his radar detector and I was using it to measure how much my voltage dips when the bass hits. I have two JL 500/1 and two MM2124 (400RMS 800 Max) a pioneer hu. I had the car in park and the readout said 14.5 volts and I had the subs turned on then I turned the headlights on and it dipped to 14.4 volts. I'm not sure if the alternator was replaced if it was could an alternator put out this much in park with subs on? Is my friend's radar detector wrong? it dips in his car. Or could there be something wrong with my cigarette lighter?

 

All is 'well' as long as u fluctuate between 14.5V-13.0V. Healthy regulator with healthy wirings keeps 13.8-14.25V on the 'northern trim' alternator.

The electrical environment is a dynamically 'living' enviro. Alternator has voltage regulator sensing the V level, adjusting to any changes. Depending on the measurement point, distances between points, wire thickness, connector amount/oxidation etcetc - u get various results.

Having any interest in car, buing a 10$ didgital multimeter is a must. Then measure voltage on different points while putting some/all applications on, u find very interesting features: measure voltage at rear lights and hit brake voltage, m. at headlights as seat seat heater, fan ...or whatever... is connected.

As u take in account all computers aboard and their minuscle input voltage levels, u start to work on the harness: http://www.cardomain.com/memberpage/748507/14

 

In other words your alternator is working fine, your friends altenator isn't working as good as yours? The less the voltage dips the better off you are. When I first install my system 5 yrs ago my voltage never dip will while in park, it stayed above 14+ volts with the volume up. Now I dare not crank up my system while in park. With a load like that my volts will dip down 12-13 volts will in park, but if i keep the volume at a decent level it will stay at 14+ volts all day long, in park or while driving.