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I recently had to replace an electrically dead alternator on my daughter's 2007 RAV4 at about 88,500 mi. I tried to buy the parts to rebuild but the lead time was > 5 days so i opted for a rebuild by a local company that I've had good experience with. The first rebuilt I put on lasted 1000 miles and i had to haul it home again after the battery light returned and stayed on. The second rebuilt was a Wilson which I thought might be a better quality but it started flashing the Battery light for a few seconds to a few minutes within the first 3 starts after installing it. I monitored the battery voltage for a few hours as I drove and noticed that it varied a lot more than my 2010 or 2001 Camrys. I was not okay with this as my daughter lives 7 hours away and drives a lot, in areas with little or no cell coverage.

So I went back and got a Denso Rebuilt as that was the OEM brand and with that one I noticed a similar voltage variation from 12.25-14.45V depending what I was doing with the gas pedal, but no battery light flashes. I did a google search and then read about smart charging systems that off load the alternator during hard accelerations and steady driving when the battery is near full charge, and load it up when deccelerating in an effort to save fuel. It would seem that the first two rebuilts did not have the correct voltage regulator to handle the signals from the ECM that manage the smart system. It is up to 1500 miles now on the Denso and so far so good. Hopefully that will lick the problem...
 

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Welcome, and thanks for your report. Hopefully the first and second rebuilt alternators were guaranteed and that you were refunded your costs for both.
 

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Thanks for this information, I'm sure it will help others when they search for alternator fixes. Do you know which Denso unit they put in? Reason I ask is that in the States we had two different alternators, one of which outputs quite a bit more amperage for accessories and was included with the tow prep package here. I believe in Canada all vehicles were equipped with this package as a default and that would be helpful to know
 

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Sorry for resurrecting an old thread, but I have an issue where I would like some help.

I have a 2007 RAV4 with V6 engine and towing package. Recently I was playing with my Scangauge, which I use in a gauge mode to show me 4 parameters at once. One of these parameters was a vehicle voltage. I have never monitored the voltage before. To my surprise the voltage is fluctuating from 12.2 V to 14.5 V when driving the car. It depends on the position of my foot on the gas pedal. With my foot off the pedal and vehicle coasting the voltage is 14-14.5 V (battery is charging). When I drive steady on the highway, the voltage is around 13 V (practically no charge, but alternator provides output). When I accelerate, the voltage drops to 12.5-12.2 V (no charging at all, I am driving on a battery). There are also plenty of conditions, where the voltage has a mind of its own - it does not obey any rules.

It is very similar to the OP description above. I have looked at the service manual and wiring diagram, but could not find a good explanation. It looks like my alternator is controlled by ECM with the help of Battery Current Sensor. I do not know what is it programmed to do and I feel a little uneasy driving long distances knowing I am driving on a battery power.

I wonder if any one of you did the voltage monitoring while driving. What was the outcome?
 

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My car's alternator died. It's a 2008 RAV4 Sport 4wd with the 2GR-FE 3.5-liter V6. The battery light came on upon start and then stayed on. I did a quick video how-to with some tips on how to remove the alternator. Here it is.

 

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I did a Alt Replacement on my 07 Rav about a year ago, I went with the Denso and so far, no problems. Replacement was pretty easy.
 

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I did a Alt Replacement on my 07 Rav about a year ago, I went with the Denso and so far, no problems. Replacement was pretty easy.
I replaced mine two years ago with a Denso 210-0656 alternator. It was remanufactured. I was hoping it would last a long time but within the last two weeks, I notice some days, the voltage would be 14.1-14.2, which is what it should produce, and other days, it would stay at a constant 13.4-13.9 volts. Is this a sign that the alternator is dying? The original alternator that I had when I purchased the car new was also a Denso and that alternator lasted 10+ years.
 

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I have noticed that our lights dim right before we come to a stop at night. Sounds right in line with what has been posted.
 

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The "smart" alternators will do that. Every manufacturer switched to those in mid-2000s.
The only time they will output full charging voltage of about 14.2V is immediately after engine start-up, at idle, to recharge the battery.
In driving they will try to keep a "floating" voltage of about 13.6 V.
 

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The "smart" alternators will do that. Every manufacturer switched to those in mid-2000s.
The only time they will output full charging voltage of about 14.2V is immediately after engine start-up, at idle, to recharge the battery.
In driving they will try to keep a "floating" voltage of about 13.6 V.
Fake news! Its not supposed to go down to 13.6V. It's supposed to stay at 14.2V or around that range. I know this because when my alternator was new, for the past 2 years, it never went down to 13.6-13.8V. It would always stay above 14.0V.
 

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And if your base model 2006 does that, you deducted that every other car, every manufactured year, does the same?
The cars with "dumb" alternators have power for the charging via the 7.5A fuse labeled "Alt-S". The rest of alternators don't need that fuse.
From my diagrams looks like the V6 always has the smart alternator.

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If the alternator charging voltage is always at 14.2 or 14.0V for a 12 volt battery even when the battery has been fully charged the result, depending partly upon the charging amperage, generally will be an overcharged battery, which will shorten battery life as the plates will overheat and the H2O component of the electrolyte will evaporate rather quickly even with a so-called "sealed" battery. It also could shorten alternator life.
 

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The recombination process in modern VRLA batteries prevents that. There's no evaporation of water anymore.
They are electrolyte starved, compared with old school batteries.
 

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I was a battery QA and RMA tech for a major battery manufacturing company. Recombination or not, automotive and other batteries which contain a liquid electrolyte have a safety valve to prevent a battery explosion in the event that a buildup of internal gases exceeds the ability of the battery to process them internally. That also includes AGM batteries. Overcharging can result in excess gas (H2O) being vented.
 
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And if your base model 2006 does that, you deducted that every other car, every manufactured year, does the same?
The cars with "dumb" alternators have power for the charging via the 7.5A fuse labeled "Alt-S". The rest of alternators don't need that fuse.
From my diagrams looks like the V6 always has the smart alternator.
Makes sense. I didn't know alternators are supposed to fluctuate like this. Must be that I installed a new battery a few weeks ago so the alternator doesn't need to work as hard. Anyway, I just hope my alternator isn't dying. I was half-thinking about getting another remanufactured Denso alternator just to be safe. I've had alternators die on me while driving. Not good.
 

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You can look and see if you have that fuse (from above) installed. If it is, the alternator voltage should not fluctuate, it's the "dumb" one.
 

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I was a battery QA and RMA tech for a major battery manufacturing company. Recombination or not, automotive and other batteries which contain a liquid electrolyte have a safety valve to prevent a battery explosion in the event that a buildup of internal gases exceeds the ability of the battery to process them internally. That also includes AGM batteries. Overcharging can result in excess gas (H2O) being vented.
That excess gas would I think be H2 or hydrogen, not water.


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The major result if the battery is being overcharged is that the plates overheat and the H20 component of the electrolyte has a lower vaporising point than does the H2SO4 component and so would be exhausted first if the vapor pressure level exceeds the ability of the battery to deal with the problem. It is interesting to dissect a battery which has been overcharged and failed as a result - burnt and crumbling plates, some electrolyte usually remaining unless the overcharge has been severe.
 
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