I have 95 SC400 and replaced my battery and alternator after my battery light decided to come on while i was trying to get to work last week. After i changed everything the battery dummy light came on like usual but turned off after the engine started like normal. But know my car has started rapidly draining batter after being off for a couple hours and its never had this problem before.

I checked the voltage of the battery while the car is on and its 13.5 volts so i know the brand new alternator is working and it doesn't die during driving. The battery warning dummy light doesn't turn on when the key is in auxillary power like its supposed to out of nowhere now.

I don,t know how i could,ve introduced a parasitic drain somewhere in the circuit buy maybe it has something to do with the battery light now? maybe it has just blown its bulb? anyone got any ideas?

 

My guess would be, you disrupted something unrelated that is in turn causing the voltage draw at key off. I would start by going over everything in the area of the alternator, since that's where you would have done most of the work.

I can't imagine a battery warning light would draw enough current to drain a new battery in a couple hours. Something much more sizable has to be running.

 

Also, new batteries are kind of notorious for just being plain ****ty. It might be worth taking that new battery back and having them test and possibly replace it. I just had to do that on my Cressida.

 

*SOLVED*
Okay so i figured it out a couple of days ago.
Bear with me here.

So when I first replaced my alternator i noticed there was no clip that connected 3 different wires into the back of the alternator.
It looked something like this.


There were only three of the prongs that would connect into the alternator. (this is a picture i took after fixing my issue and how they should correctly sit)

When i first went to replace my alternator i didn't know if a clip was supposed to be there or not and didn't have enough time to do research as i daily drive this car back and forth to work and i had to get it fixed asap. When i first took the alternator off i tried to keep the 3 wires in the same orientation but during the scuffle of scooting the old alternator out and moving the new one in they most likely got swapped around.

This is how i made the wires up originally after replacing.

Please note this is the incorrect position for the wires, the first picture is the correct wire orientation.
Doing some research on the forums i found this post from back in 2019 https://www.clublexus.com/forums/ls-...-pig-tail.html.
Within the post they discussed how there WAS supposed to be a clip holding in the wires and also gave a handy dandy diagram showing exactly witch orientation the different colors were supposed to be in.
After connecting the wires in the right orientation the battery light now comes back on and the battery no longer drains.
Boy do i feel dumb.
In conclusion my hands are a little greasier, my back in a little bit more pain, but im a bit smarter now for it. Thanks for the help guys, especially the people from the older forum post. Hope this can help someone in the future.

 

I should go buy that clip now xD