1999 Lexus ES 300 Alternator

Tiny
AZVACS
  • MEMBER
  • 1999 LEXUS ES 300
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 85,000 MILES
I am on my 3rd alternator in 3 weeks. After a couple of days, the output voltage drops below 12V. What is the issue?
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Sunday, August 22nd, 2010 AT 8:25 PM

11 Replies

Tiny
WRENCHTECH
  • EXPERT
Are you charging the battery with a battery charger before installing the new alternators?
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Sunday, August 22nd, 2010 AT 8:47 PM
Tiny
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Yes
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Monday, August 23rd, 2010 AT 11:58 AM
Tiny
WRENCHTECH
  • EXPERT
Then you probably just need to buy better quality parts. There is a lot of junk being sold out there at these discount houses.
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Monday, August 23rd, 2010 AT 12:04 PM
Tiny
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I am now on the 4th alternator and the 2nd battery.
2 reman alternators from Auto Zone and 2 from Napa.
What the heck is going on with this car or is it just bad parts. I had the 3 alt checked at NAPA before I installed it and it checked out good. After I had another starting problem, I pulled it out and took it back and they bench tested it and it passed. I reinstalled it and took the car there and had them check it and it failed. Only putting out 12.2 at idle.
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Monday, August 23rd, 2010 AT 12:05 PM
Tiny
WRENCHTECH
  • EXPERT
Now the explanation is different. I was under the impression they worked and then failed but if they never worked at all, then your just misdiagnosing the problem and the alternator is not the problem at all.
Check all your fuses and maxi-fuses.
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Monday, August 23rd, 2010 AT 12:18 PM
Tiny
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Fuses are regulating the voltage? Which ones?
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Monday, August 23rd, 2010 AT 12:20 PM
Tiny
WRENCHTECH
  • EXPERT
It's best to just check all of them using a test light. Don't forget the main 100amp one.
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Monday, August 23rd, 2010 AT 12:38 PM
Tiny
AZVACS
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I just installed the 4th alternator. It's output read 14.28 volts. I drove the car for about 10 miles and now it's output reads 12.2 volts. Is this normal or has the car burned out the regulator in the alternator also?
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Tuesday, August 24th, 2010 AT 12:15 PM
Tiny
WRENCHTECH
  • EXPERT
Your burning out alternators. You either have a bad battery that is causing them to max out or they are just junk alternators. There really isn't any other explanation.
Going back to my first post though, if you are not fully charging the battery manually before starting it up with a new alternator you will overload the alternator and burn it out. They are not designed to work at maximum output.
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Tuesday, August 24th, 2010 AT 12:28 PM
Tiny
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The battery is brand new and fully charged prior to installing the alternators. The last 2 alternators were from NAPA. I assumed they had better parts than the discount stores.
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Tuesday, August 24th, 2010 AT 12:40 PM
Tiny
WRENCHTECH
  • EXPERT
I don't know what to tell you. If you are sure they are burning out, overloading or substandard parts are the only external causes of that.
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+1
Tuesday, August 24th, 2010 AT 12:55 PM

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