Low voltage at idle? Common?

[gmrulz4u]

OK...quickly here(because I posted earlier as well)

 

I have an 89 Supreme, a upgraded 160amp alt, an Optima Red Top battery with 800 ColdCranking amps($300!), both only a year old, plus changed the power and ground wire to 2 gauge.

 

I have a digital voltmeter(aftermarket), and when it's anything below 70 degrees faranheit(20 celcius), the voltage is anywhere from 11-11.8 volts when at a stop and idling. The reason I mention the temperature is just because it's worse when it's not "super" hot out. When it's really nice and hot out, the voltage is at like 13-14 at idle!

 

I read before that an alternator produces a lot less voltage when at idle, and that there was some cures for it, but I can't remember what they were? Something to do with making the pullies smaller or something!!??? I can't remember...

 

So is this normal, or should the voltage always be atleast 12.5 at idle? Especially seeing as my stereo is barely loud, and I have heat or A/C turned on when it goes down to 11.2

 

THANKS ALL:o)

[chronic139]

i just replaced my alternator and my car is doing the same thing. I dont really remember if it did it before. Im not worried because i have 5 year warranty and I did it myself. If it dies, Ill do another one.