2000 Lexus Is 200 Voltage /charging Fluctuations

[roop999]

I recently noticed that on my voltmeter @ idling 750-850 rpms my voltage was very low if AC and lights on - around or just under 12v. Then i started getting poor performance from the car during acceleration (2000 lexus is 200 automatic)

got it checked out by an auto electrician. The alternator reading was 13.6 v at idle speeds but dropped off to 12.7-12.8 v when Ac and lights put on. The alternator was thought to be the problem. The grounds were checked, the alternator belt was ok and the Battery was 12.8 v with car off.

I then went on to try used alternators . 3 of them to be exact - same problems !! Exact same voltage under loads- 12.7/8 v .

Eventually i just put back on my original alternator and sometimes @ idle under load the voltage is fine 13.8 v Then sometimes loaded it reads around 12.7 volts.

And by the way i also tried 2 other batteries and same problems!

Anyone had similar problems or can suggest a solution?

Is it that the voltage on the is 200 goes up with rpms as per normal or is the voltage regulator bad in all 3 alternators???????

I plan to change the belt and check the difference. But i am lost!!!

Someone suggested to check all the fuse terminals and clean them out because of increased resistance ?? Lost guys . Please help !!!!

[roop999]

And just further information. I changed windscreen 3 months ago and then experienced a problem with the automatic lights they dont work anymore. I manually turn them on and strange enough they now go off when the driver door is opened and car is off. Do you all think that there may be a small leak of water into my electrics. I actually asked my auto electrician to check this before and he said no water seen around terminal on driver side, but i didnt observe for myself. What exactly to look for in this case and can water in the electrics cause this fluctuation i am having?

[VLM]

With the engine at idle, the alternator is having to keep up the 14 odd volts at a slow rpm. Add a high electrical load and it can struggle at the IS's slow 600 rpm idle. Does the voltage come up to normal by about 1000rpm?

Most cars idle at 800-1000 rpm and the alternator can handle this. I've noticed on mine that with all the electrics on the voltage dips a bit on idle.

Sounds like the alternator's not the problem, but something else is loading the electrics.