Looking for help. I have put 5 new alternators and 6 new batteries in my 2001 ES 300. I have also replaced the connection and ruled out a parasitic draw. The alternator WILL charge when idling without loads on but WILL NOT charge when loads are on. So if I pull up to a stop light with my lights and AC on, I start to lose power and everything goes dim. Toyota could not figure it out or another shop that specializes in electrical issues. Please help

 

Where are you getting the alternators? I went through four (?)alternators in a few years from O’Reillys until I went and go another proper Denso rebuild at NAPA.

If an alternator isn’t making the required Voltage, that’s an alternator issues. It’s a stand-alone component free of any computer control on that car. You can measure the Voltage across the alternator’s output terminals and confirm that.