I have been having an issue with my alternator and sourced one from a junk yard. The problem I been having is that my batt light comes on and only goes off when my engine idles extremely low. I got the donor alternator out of a 93 gs300 and my car is a 92 sc300. I was wondering if anyone my have the wiring diagram for the alternator or can tell me which are the white, black/yellow, and yellow/green wires are. Have anyone has this problem before and if they have had a solution, what they do to fix it

 

Have you checked the battery itself? Not just the voltage, but also the load rating should be checked...

 

^^ OP, I highly recommend this as rentaro suggests. Also get the alternator you will be using checked. You want to be sure it has a good voltage regulator as well as good amperage output. Alternators usually fail in such a way as to have very low to no output but their voltage regulators can also fail so as to cause an overcharging condition which can very negatively and even dangerously affect your battery over time.

Here is a screenshot of the early 1992-1994 SC300 alternator wiring schematic. As you'll see in the picture, the older style round alternator plug is shown.

 

Hi, I just wonder if someone could help with an issue that comes often at my Lexus 73/ SC300. Many time after couple days in garage I found that the battery is full discharged despite all lights are switches off and the starting key are removed. That happens not always but exact when I need the car discover that the battery is completely dead. The period that do not use the car and is on my Garage is randomly and never I'm sure that. when I need the car could start it!
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sounds like a draw issue or if the car sits for too long like weeks at a time before you drive it, then the KAM (Keep Alive Memory) would be your source but its normal to do so. If you're not driving the car often and it sits then I must recommend installing a battery disconnect or the cheap way, disconnect the negative terminal or entire battery, whatever you're comfy with.

 

Thank you very much, I'll follow your advice because is easier one to implement