Hello everyone, My 91 ls400 died while exiting the freeway a few days ago. First my stereo went out. Then all these warning lights started lighting up like I'm about to start my car. Finally as I exited car dies. I assumed it was the alt. I have had problems with diffrent alternators in the past so I'm familiar with the symptoms. So I sent my alternator to be rebuilt and upgraded to handle higher load. But before I sent it in I had autozone test and they said the alternator was good. I went ahead and sent it anyway cause regardless I was gonna send it in to be upgraded. So I get back the alternator install it tried to start the ls400 up, but wont start. took the battery to get charged in autozone. After about an hour and a half battery was charged to 33%. Go home put the battery in, crank it up engine starts up. Hallelujah! Or so I thought after about 5 min of idling in park stereo starts powering down. Dash warning lights are on. car was looking like it was gonna die like before. this is my first ls400 so my knowledge although growing is apprentice lvl at best. So can anybody help me figure this out. alternator is rebuilt to be better than the old one and the battery even thou not charged all the way. car powerin down while running rules out the battery in my opinion. any help/advice is deeply welcomed thanks everyone!

 

Did you check the voltage at the generator's +B terminal and the battery post?