I have a 93 Sc400, love it. Except now it is acting up. The battery light came on just the other day sooo I believe Monday. Today is Thursday and I replaced the battery tuesday because the battery light came on and when I got home and came to a complete stop the battery light would come on and then I turned it off and it wouldn't turn back on. MY friend jumped it so then it worked. Later it came on again when I started driving. Alternator? I got that checked out and everything was fine. Ground wire? I checked that and all was fine there. I checked the alternator wire from the battery and there was some grease leaking onto the alternator. I assume leaking because there was grease on it. Then we just checked those two connections from the battery and on the way home.. the radio died out. I unplugged the deck and sat in the driveway. Reved a bit and then still it acted very weak. Turned on... did not turn on. Just put it on a trickle charger and it says the battery is completely dead. The battery was checked by Schucks and they said it was fine and a good battery. I bought it from motion auto supply. I do have 2 amplifiers hooked up but I disconnected the deck which disconnects the amps and still the light was on. Then I even took out the fuses just to be sure. Still nothing... I replaced the serpentine belt as well since the old one was a bit cracked and to be honest... I am desperate and may just rage sell if I can't figure it out. I don't want to take it to Lexus because they will overprice me just to tell me what the problem is. Thank you all!

 

Just have the alt tested at an auto part store.

 

I did have it tested and it passed...

 

BAttery has ben on trickle charge literally all day and the 25% light just now came on.

 

If the shop diagnosed the alternator wrong, I'd suspect the diode packs on the alternator, but if they checked the diode pack specifically on the alt, I guess the logical answer is that you have a large drain somewhere, like wires crossed, or ground wires touching...

 

Have you tried a parasitic drain test?

Disconnect positive battery terminal side, measure the voltage from the terminal to the cable. If this reading is too high your battery is constantly being drained from a component, as touched on above.

 

Have your alternator tested at a shop that actually rebuilds alternators (they'll usually let you watch the test too). The tests done at places like autozone using a bench top computer or portable testing unit can often pass a failing unit...it's happened to me twice.

 

I'm thinking alternator too. Probably starting to go bad and killed the battery

 

You dont need to take it to Lexus. As mentioned before any alternator/battery shop will be able to diagnose it for you properly, not some kids.
After installing my carPC on my old '99 I had the same issue, some sort of paratitic drain that I could not locate, and testing the battery & alternator showed they were fine. Took it to my audio installer and he said there was no excess drain on the sysytem due to the carPC and no parasitic loss. I finally got fed up and just bought a new battery and a rebuilt alternator, had no issues after that.

As for the grease on the alternator, dont older 400's have the power steering resivoir located directly above the alternator? From what I remember it leaks onto the alternator and causes them to fail. You could look for that as well.

 

your power steering is leaking fluid on your alternator, you need a new alternator

same problem I had last summer

 

So what does it mean if the battery dies when the car is off?

 

Put a new alternator in it. Runs fine. But there was grease or PS fluid on it. Won't the same problem happen overtime?

 

Yes. like ***** mentioned, your PS leaked onto your alternator which caused the failure most likely. You need to fix the leak or your existing alt will go bad.

 

Your alternator is also 20 years old. Just replace it and go from there