Was wondering what the voltage should be at idle. When under load my Voltage drops to 12.7. And never gets to 14.1. Checked all connections and grounds. Even fuses. Cannot find any problems. My other cars stay at 14 volts when there's a load. This one starts to slowly decline from 13.7 or so to 12.7 it climbs back up a little when the rpm's go up. But never 14.1. I charged the battery separately then start the car everything is fine. Even the first few minutes with a load it stays at 13.9 to 14 volts but then after a little bit slowly reduces and ends up at 12.7 is this normal the part is from car quest. My dad thinks maybe it's just a bad design and the alternator is set up to work that way cause it's generic. Sounds fishy to me. Replaced this 3 times and all do the same. Even brought the last one to be tested out of car. It passed. Does anyone know if the factory alternator works this way? Hellllpppppp

 

I had a similar problem with my 2000 sienna. Read here.
https://suite.io/vincent-ciulla/w9326x
However I did not want to have a high idle because I do not like having the car jerk when I put it in gear. So what I did instead is I obtained a slightly smaller alternator pulley (I think that is all that Toyota had done to there "improved alternator design") I did have a hard time finding one and I had to machine mine a little to make it fit but it worked beautifully and made 13.9v at idle with all accessories on. An idle speed adjustment is a much simpler fix but it requires the ECU to be programmed by the dealership. Your local toyota or Lexus dealership should be able to set you up for under a hundred bucks.

 

I got one of those cigarette lighter voltmeter's the LS400 guys suggest.

The lowest I get [sporadically] is 12.3-13.1, and that is with A/C, my HID's and sound system going. And as you said, as I'm slowing down/idling.

Normal operation, that I monitor is the 13.2-13.9 mark. I've seen 14v once, since I installed my little voltmeter.

Honestly, your dad is right, along with many other members on here. The 80amp alternator was an oversight on Lexus' part sticking it in the Camry & ES class, yet the 'base' ES already has more additional items causing more strain on the charging system than the Camry.

All other models got higher Amperage alternators. Avalon & Sienna - 100amp, and Highlander [depending on trim] was 100- 130amp

 

after a few weeks of battery light problems I went back to the compressor and found the plastic heat shield on the negative cable was cracked and gave a little play even though bolt was tight after repairing and getting a good connection I have almost 24 hrs no batt. light.........will post again if it didn't work