Has anybody ever heard of FOUR...yes FOUR alternators going bad. I have to admit the original alternator and first replacement probably went bad because of a leaking power steering pump. However I replaced it prior to install of the second replacement which went bad but now I am just baffled because I just replaced the third alternator and it seems to be going bad also. I just installed it yesterday no problems and battery was fully charged and read 12.5 volts or so using a multimeter. Decided to start the car and alternator went to 13.59 to 13.65 volts put the HIDs on stayed around the same, turned the heater on high and the HIDS on went to around 13.2 then back to 13.59. Drive the car to work today seems fine, drive home and it's dark turn on the HIDs get home leave the car running, check with multimeter and it's at 12.89 and dropping!

My check engine light came on but it's for an oxygen sensor according to my code reader.

Changed the plug to the alternator because it was cracked.

1999 LS400 Platinum Edition

 

OEM or aftermarket?

 

Sounds like the battery isn't holding charge correctly. How old is the batt?

 

bosch was the original alternator and napa have been the last three replacements and the battery is 2 yrs old.

 

Have you check the batt/? Thats insane, the battery has to be on its way out, i cant see it any other way...

 

the battery reads 12.5 to 12.75 w/o the car started.

 

https://www.clublexus.com/forums/ls4...-searched.html

Check the usual:
Battery cables and for any power accessories that may be draining the battery when the car is off. I suspect battery.

Your HID's factory or aftermarket? If aftermarket, are they wired up right? Some of those aftermarket won't run/start from the factory harness so if you tapped into a constant hot or "on" hot and it is shorting this may be a factor.

 

WOW , Strange.... You got me,

 

no HIDS are factory also never been touched.

 

+1 on battery ive seen my battery hold 12.5v - 13v and not crank my car. The problem was because the cells fail and i didnt have enough cold cranking amps. I say if you can go to autozone, pep boys or kragen and tell them to do a load test on your battery.

 

If you didn't replace the lines when you replaced the powersteering pump it could be causing the leak onto your alternator.

 

Sounds like a dead cell in the battery. Have the battery load tested at you local auto parts store. Also, and this happened to me after I went the 5+ alternators (PS was not leaking,,had been fixed prior), check your grounds. In my case, it wound up being a loose ground leading to the plug that goes directly into the alternator. I was killing OPTIMA YELLOW TOP batteries, which is almost unheard of, expecially since I don't have alot of audio installed besides a sub.

 

There are people who have experienced the similar problem like you, ABRA, in Japan. It was discussed once or twice at the Japanese Forum "Celsior Up" regarding the aftermarket alternator issue. http://celsiorup.com/

Those non genuine alternators tend to fail in hot summer here. The aftermarket alternator which uses non Denso's regulator is not strong enough against the heat in hot summer. Denso's regulator has a tall heat sink and it dissipates heat properly and endures the high temperature. But the aftermarket one does not have a tall heat sink and it is weaker and it can not keep the voltage when hot. It keeps a little higher than 14 volts when cold but it becomes less than 13 volts quickly when ambient is higher than 80degrees F or more. Lexus LS400 or Celsior's engine compartment tends to have higher temperature than other average cars and the alternator needs a capability to be OK at higher temperatures. I don't know Napa's one but I don't think it uses the regulator supplied from the Denso. Does it have a heat sink as is shown the photo which is Denso's? The heat sink is located top left side with a tall heat sink.

 

A battery has to be load tested to confirm it is bad or not. You can not just put a volt ohm meter on it and call it good cause you get 12 volts.

 

I second this! May show 12 volts with no load, but drops intensely under load when a cell is shot.