Alternator Problem?? Please Help

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Jul 21, 2009 | 12:39 PM

jcjr

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Joined: Dec 2005

Posts: 228

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From: AZ

Alternator Problem?? Please Help

Hello All,

I have a 2001 RX with 82k...I have had to jump start the car twice in the last month....

The first time we thought that the rear hatch had not been fully closed...Second time we have no "reason"

AAA guy jump it today and told me that alternator was ok but that battery was at "half-life"....

Went to Autozone and had them check the battery(Duralast Gold)....they said battery is fine but alternator only putting out 50 AMPS instead of 100 AMPS...

Any thoughts or suggestions would be appreciated!

Jul 21, 2009 | 01:12 PM

lexus114

Lexus Champion

Joined: Aug 2007

Posts: 4,507

Likes: 38

From: Bethlehem Twsp. Pennsylvania

Quote:

Originally Posted by jcjr

Find out how many volts its charging at i.e 13.6

Jul 21, 2009 | 02:13 PM

bob2200

Driver

Joined: Mar 2002

Posts: 1,800

Likes: 13

From: Maryland

Quote:

Originally Posted by jcjr

alternator only putting out 50 AMPS instead of 100 AMPS...
Any thoughts or suggestions would be appreciated!

One of the diodes in the alternator failing would be consistent with a drop in output.

Jul 21, 2009 | 06:13 PM

jcjr

Thread Starter

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Joined: Dec 2005

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From: AZ

Thanks for the responses....I am confused by the 2 differing opinions....battery versus alternator

I may take it to Costo for a third opinion....

Jul 21, 2009 | 06:28 PM

bob2200

Driver

Joined: Mar 2002

Posts: 1,800

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From: Maryland

None of the Costco's I'm familiar with (East Coast) have any equipment for checking batteries.

I don't think that the responses point in different directions. Checking the charging voltage is checking the charging system primarily.

I think it would be helpful to go to some place that has an electrical testing machine that puts the battery under load and then measures the current it takes to recover the charge, etc. Years ago, Sears Auto Centers used to be the place to go. These days, there may be even more sophisticated equipment. I haven't had electrical problems with a car in the past 20 years.

Jul 21, 2009 | 07:18 PM

jcjr

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From: AZ

Thanks BOB2200

I was not sure about Costco....

The autozone guy did put a load on the battery and the battery checked out OK....He then tested the alternator at 2000RPM and got "50 AMPS" of output.....

I was not with the car when the AAA guy tested...it is primarily my wife's car...but the AAA guy according to my said "HIS TEST" of the alternator was OK...again I dont know excatly what he did....

I guess I have to find some other place for a third opinion.....

Thanks again

Jul 21, 2009 | 08:57 PM

salimshah

CL Community Team

Joined: Apr 2001

Posts: 16,560

Likes: 1,385

From: Austin, TX

From $&sense point of view, just buy a $30-$50 battery.

Otherwise you can pull out the alternator and have it tested on the jig. If you are not getting a discharge lamp turn on, your alternator is good.

Although alternators can go bad, but RX alternators are pretty stout.

Salim

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Jul 21, 2009 | 11:45 PM

code58

Lexus Champion

Joined: Feb 2008

Posts: 1,709

Likes: 16

From: Ca.

Quote:

Originally Posted by jcjr

jcjr- I think the AZ guy led you astray. Even if a battery is low, it's gonna be 1 rare day that you see a 100A alternator put out 100A. About the only time it's going to do that is at least the RPM that he tested it at, and then if the battery is really low and you have everything in the car turned on. If the alternator was putting out 100A without a lot of that amperage flowing on through to stuff you've got turned on, it would cook that battery in a hurry. You can't stuff that kind of amperage in a battery without overheating and warping the plates bigtime. With a battery that's dead and jumped to get it started, you might see close to the rated Amps VERY briefly (a few seconds), but it's gonna have to come down from that pretty fast or you're gonna be buying a battery anyway from turning it into an oven. I think the 50A that he saw would be pretty normal for a battery that had SOME juice in it and not a lot of electrical on. Some, yes , but I doubt that you had everything turned on that the car has in the way of electrical. My 25A "smart charger" cycles off and on even when a battery is fairly low, to keep it cool and prevent any plate damage. If that thing were a 100A charger it would have that battery smoking and headed for the junk pile in no time.

Jul 21, 2009 | 11:49 PM

#10

code58

Lexus Champion

Joined: Feb 2008

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From: Ca.

Quote:

Originally Posted by bob2200

One of the diodes in the alternator failing would be consistent with a drop in output.

Very true! Any decent electronic battery/starter/alt. tester should do a diode test in full test mode. I know my OTC does and I would think the AAA guys should... but who knows?

Jul 22, 2009 | 07:15 AM

#11

mikey00

Lexus Test Driver

Joined: Jul 2001

Posts: 959

Likes: 2

From: New Jersey

I would go with the battery and move on. The odds are with the battery. It's cheaper than any troubleshooting you are going to do and almost guaranteed to fix your problem. It seems this problem comes up often on the forumn. The battery load tests fine so the suggestions come in to check alternator, starter, standing current draw etc but it seems like it's always the battery that fixes the problem. I am not saying this is always the right thing to do but with the RX you at least know where the odds are.
I do remember one time a few years back where one member had a standing current draw problem and the dealer replaced the body control module to fix it. So I guess there are other possibilities.

Jul 22, 2009 | 11:55 AM

#12

Barryst

Driver

Joined: May 2005

Posts: 144

Likes: 1

From: MA

I had my altenator go on me a few months ago, my battery light came on. but it was intermitten, I could "feel it" my car would be sluggish, (with battery light on) then it would pep up, and the battery light would go out. I put a voltmeter across the battery while it was running,(battery light on) and I was only putting out 9-10 volts. Took it out of car, brought it to Autozone to have it tested, and they said it was good! Like I said this was a problem that was coming and going, so I changed the altenator. My lights are now brighter than ever, and the car performs better also, and my battery light never came back on.- Hope this helps.

Just my two cents....

Jul 22, 2009 | 07:58 PM

#13

jcjr

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From: AZ

Thanks everyone...

Hey Salim what do you mean by a discharge lamp???

I have had no warning lights on the dash.....

Again we are pretty sure that the rear hatch was left open the first time we had a problem...

The battery is a Duralast Gold that is an "8 year" battery....It is only three years old....

The first year the car was in Phoenix for extended periods of time without use and I would disconnect the battery while I was away...

The last two years the car/battery have been in regular use...

I am on the fence about what to do....

Jul 22, 2009 | 09:03 PM

#14

salimshah

CL Community Team

Joined: Apr 2001

Posts: 16,560

Likes: 1,385

From: Austin, TX

It is sort of double negative ....

There is a warning lamp that turns on, when the battery is not getting charged. The first time you move the key to run, make sure all your warning lamps in dash turn on. When you start and the engine runs the lamp should turn off.

With a die-hard battery and the warranty, just drive up to Sears and let them have a look. You can drop the battery with them for an overnight charge. They can test your alternator too and if needed get you the replacement battery (under warranty).

Alternator belt might be loose. [you should see the discharge lamp in the dash light up]

Salim

Last edited by salimshah; Jul 23, 2009 at 07:20 AM.

Jul 22, 2009 | 09:41 PM

#15

code58

Lexus Champion

Joined: Feb 2008

Posts: 1,709

Likes: 16

From: Ca.

Quote:

Originally Posted by jcjr

See if there is someone else who will test it for free (load test). But make sure it is charged up 1st. Some testers will load test a battery with low voltage and some will only test if it is fully charged. It will tell you to charge and retest if it is not sufficiently charged to test. AZ has the equipment to test, I just feel they often don't have people with much knowledge doing the testing. A load test is so simple and takes only a minute to do, really I would think most anyone with the equipment would do it, just for good PR. If it load tests good by someone else, i would forget about it unless you have more problem. After all, you said you thought the rear hatch was left open. Sometime we think too much about these things.

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