alternator woes
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Driver School Candidate
Joined: Jul 2011
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From: Vermont
alternator woes
My issue is with my alternator...I think...
1st thought the battery need replacement, then both the battery wires, then found out there was no charging from the alternator. Replace that & still only charges for the 1st 15 warm-up minutes. Then I have to play with the throttle to keep it from stalling, to find that by this time it's only running straight from the battery till it stalls. Could it be th new alt. is a faulty alt.? I hope so.
My ride is a 1991 LS400, No mods, all stock. with just over 200k on the ticker.
Pole Position
Joined: Apr 2011
Posts: 319
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From: az
sounds like a garbage alt.
or everything isnt hooked up properly.
check voltage out of the alt and compare to voltage at the battery.
if the voltage is 13.5 or less from the alt, replace it again/warranty
13.8 v to 14.10 is ok.
13.8 is marginal...its borderline ok/not ok
and check with headlights on high and ac on......creates the most load/draw from the alt
or everything isnt hooked up properly.
check voltage out of the alt and compare to voltage at the battery.
if the voltage is 13.5 or less from the alt, replace it again/warranty
13.8 v to 14.10 is ok.
13.8 is marginal...its borderline ok/not ok
and check with headlights on high and ac on......creates the most load/draw from the alt
Pole Position
Joined: Dec 2009
Posts: 3,278
Likes: 317
From: ct
Sounds like emarknot is right; bad bat, bad alt, or the wires don't have a good contact. (bad ground) If you need to raise the RPMs to have the alt charge then you need a new one. Does your power steering pump leak onto the alt? How old is battery and alt?
Thread Starter
Driver School Candidate
Joined: Jul 2011
Posts: 2
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From: Vermont
Alt. is new, Battery is new, & the wiring to/from the battery is new...Charge is fine (14.24) @ start up, But it peters out & stops charging Period after about 15 min. or so. 
You know what the real kick in the head is...? I brought the alt. back to where I bought it to get it tested, & it passed... I think I'll just get another to see if this one is a Junker alt.
You know what the real kick in the head is...? I brought the alt. back to where I bought it to get it tested, & it passed... I think I'll just get another to see if this one is a Junker alt.
Last edited by wolver1ne5; Jul 20, 2011 at 07:21 AM.
Pit Crew
Joined: Feb 2006
Posts: 197
Likes: 2
From: NJ
There may be nothing wrong with the alternator. Are the belts in good shape, and are they turning the alternator normally after those 15 minutes? If the belt is normal, then I would suggest doing a voltage drop test to see if there is excess resistance between the alternator and the battery. With the engine running at 2000 RPM, find out how many volts you're dropping between the alternator B+ terminal and the battery positive terminal To do this, connect the red lead of a voltmeter to the alt B+ terminal (the one with the big cable attached to it) and the black lead to the battery's positive terminal (make sure you are touching the battery terminal and not the cable clamp). This should be less than 0.7 volts. Anything higher than 0.7 volts means that there is too much resistance somewhere between the alt and the battery - could be dirty connections corrosion, the wire itself, etc.
Then do the same to the ground side, i.e. connect the red lead of the voltmeter to the alternator's case, and the black lead to the negative battery terminal. Voltage drop on the negative side shouldn't be more than 0.2 volts. Hope this helps.
Then do the same to the ground side, i.e. connect the red lead of the voltmeter to the alternator's case, and the black lead to the negative battery terminal. Voltage drop on the negative side shouldn't be more than 0.2 volts. Hope this helps.
Last edited by 91LS400vgb; Jul 20, 2011 at 11:27 AM. Reason: typo
Driver School Candidate
Joined: Nov 2009
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From: texas
I have a 1999 es300 with the same problem. Have tried 5 different alternators, each testing good at different alternator repair shops and parts stores. Have replaced both battery cables, seem to have good clean solid grounds.Tried switching batteries, with no difference. everything on car seems fine, runs great, ac and radio no problem. Will charge on highway driving, but ideling or stop and go traffic, it drains battery in about 30 minutes. Have had several shops check and they tell me its probably a loose or broken connection, but no one can tell me what else to check. Any one else have anything to add,would love to hear it. thanks
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Joined: Sep 2010
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From: GA
You could also have a parasitic drain going on. This happened to me and found out that it was my car alarm was the culperit. If you replaced everything brand new and still having this problem either you have an excessive load or perhaps you need to go to an higher amp alt. I got mines from powerbastards.com. If you do decided to go with a HO Altenator make sure your get a batter with high CCA reserves or get a HO Battery (Trojan TransPower ST1000 AGM 31 Battery).
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Driver School Candidate
Joined: Nov 2009
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From: texas
can anyone tell me if there is a difference between the alternators on a camry or the es300? had a alternator rebuilder tell me if you get an alternator off another type car, even if it fits, the regulators will be different and the alternator will not work with the lexus. i have gotten a couple off cars in salvage yards, and wonder if that might be the problem. thanks for any help.
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