Hi all,

So, I am to diagnose if it's either the alternator or the battery.

1) Checked that my alternator belt is running and no crack (still in good shape) as far as I can see.
2) Battery is dated as of Oct 2022, which I bought from Costco's around mid-November 2022.
3) Battery has around 12.30V from the multi-meter, when the car is not running. With the car idling, honestly I don't see the battery voltage increases to 14V plus.
4) No OBDII code reported by the scanner from my RX350. Clean as a whistle.

It's been very cold for the past months where I live in CA. So, there is a good chance the battery the battery is bad, even though 5 months old since Oct 2022.

Thoughts?

Thanks!

 

What voltages do you see?

 

I see 11.98V-12V when the car idles.

Thanks.

 

Your alternator is not charging.

 

Hopefully, it's just the belt (being old or having slippage) but not the alternator. It was fine this morning when I started the car and was commuting. Mechanic wants $700 for part and labor. Not a hard job, as I see plenty of vids on YouTube, but it's an involved/laborious job.

By the way, apparently there are two different grades of alternator, one without tow capacity/package and one with. So, the one with tow package means that it can provide 130 amp and actually is cheaper than the one without tow package. I am pretty NOOB at this part of the alternator.

Below is the image from my local Lexus dealer part department.




The below video is helpful to diagnose.


One good video on how to fix.

 

I would think that if the belt was slipping there would be issues with the power steering, A/C compressor, water pump as they're all on the same belt. I would do the belt while you're getting the alt replaced though, it was very simple for me to just change the belt myself but I haven't had to DIY an alt on this car yet, seems like a pain compared to other cars. I would personally upgrade from the 100 amp to the 150 amp 2007 Sienna alternator for a longer life (Recommended by Denso themselves)

 

​​​​@MattRX Thanks for the answer. I had the belt, the serpentine belt replaced 3 years ago by the same mechanic, but maybe I should have it replaced as well, because he has to take it out. Good point on the 150 amp. I'll make sure to get that. My local Lexus deal sells the 130 amp CHEAPER than the regular one!

For general readers...

My 2007 RX350 has only 137K miles. Man, I would think the damn alternator would last longer! :-) There is no OBDII P-code at all. My vehicle is clean of any P-code. Shouldn't there a P-code if the alternator does not charge? I just wanted to confirm (self-denial on a bad alternator ) before spending bucks on a fix.

Thanks for any thought!

Another good 2007 RX350 alternator replacement.video.

 

Gotta love the transverse engine mounting

Is there a battery light? I remember on my Highlander my dead alt would constantly trigger the battery light, but no P code, however that car is also a good 6 years older than my RX and is probably a bit more of a dinosaur electrically!

27060-0P340 (not sure if new or reman) / 27060-0P241-84 (reman)

Is for the Sienna but any 150 amp for the 2gr-fe etc will work too as long as they're not for the 2006-2008 RAV4 V6 which requires extra input from the ECU to charge.

 

Yes, unfortunately. The persistent red battery light on. My 12V battery is only 6 months old, and Costco was nice enough TODAY to let me exchange for a brand new on dated March 2023, because I told them, at the time, that I believe the battery isn't good, since I have no P-code whatsoever on a bad alternator. With a brand new battery, I still see the red battery light on.

The above parts don't fit the 2007 RX350, per my local Lexus dealer's parts web site. Anyway, I'll make sure the mechanic give my car the AMP!

Thanks.

 

They won't list as fitting the car, but according to https://as-pl.com/en/c/alternator_parts_a-p they have the same dimensions and it's a common upgrade for the Highlander owners to do. Same plug, same pulley, same fitment but I do see it is a little more expensive than the 130 amp.

 

Just for the heck of it, have you tried to remove and thoroughly clean your terminal connections at the battery? And make sure they're tight and make good contact?
Also, for the heck of it, with the car idling and the multimeter connected, try wiggling the cables?

Also, also, for the heck of it, inspect ALL cables from Battery to Alternator to Fuse Box (under the hood) for Mice damage?

 

What I'm suggesting is checking for Voltage Drop to fully diagnose a bad alternator (and eliminate the possibility of a bad wire).

Here is a better video that shows how to perform this simple test on a 3.5L Toyota:

 

Thanks! That was the first thing I did. Cleaned out all the terminals and that they are tightly fitted. I even put in a new battery. (See my post above that Costco's was nice enough to exchange my 6-month old battery with a new one.) All the cables are healthy. Car runs and starts, but, eventually it will drain the battery if it's not charged while driving.

I checked the voltage before the car turned on and during idle, which it does not increase the voltage to 14V when measured.

 

@spinellib posted the two videos of doing the resistance test on the alternator. That was *also* the test done by my mechanic. And found that my alternator has high resistance. Cost $700 with new alternator AND belt, depending on where you live. Took him nearly 3 hours to do it plus testing. Car now shows voltage climbing to 13.7-14V when idles. This job is not hard to do really but is involved and make sure you have the right tools. If you decided to do yourself, I would say to make sure to do ALL the tests first to determine that it is indeed the alternator at fault; make sure to take out the old alternator when you're ready to buy a new one! The core charge can be pretty high -- up to $200. (My local Lexus dealer has an $80 core charge.)

At the time of my car's alternator went dead, my car had 137K miles. I am interested to know if other RX350s out there had the alternator replaced at what mileage. I would think Lexus makes the alternator to last longer! My 2001 Honda still has the original alternator working at 179K and still runs fine! Very disappointed with Lexus!

 

137k miles sounds pretty good to me! My 2008 RX is on the original one still at 225k. My Highlander however wasn't as lucky, original went out at 142k.