The wearable parts are the brushes and the bearings. I have not come across a bearing issue and the brushes can last 300K miles +. Most likely the failure mechanism would be the diode (s) and they are bulletproof till the battery has a dead cell or two. So as long as your failure of battery is not due to shorted cells, you can expect the alternator to live as long as the expected life of the vehicle.
The question is why the concern about the alternator? Is it because of experience with other vehicles? Some Lexus models have alternator below the steering pump and in those, when the pump leaks, it takes the alternator too.

Salim

 

Yes from experience with other cars. I owned GM and Kia recently and they lasted 120k miles or a bit more. They went suddenly. I assume you have to replace the whole alternator not just the defective parts? Good to know so I don't have to worry about it. The battery was original, it was leaking a bit. It's was a six years old battery so it is time to change it. Not sure if the cell were shorted. The previous owner never change it. I replaced it with one bought from Costco, 700CCA. Run great now. Thanks for the reply.

 

Most commonly. I haven't known Toyota/Lexus alternators to be particularly prone to early failure (I have an 18 yr old Sienna, 290,000km with original alternator, works fine), but if bad luck hits and you don't want to fork out for a new OEM unit, you could consider a remanufactured one. They are usually quite a bit less expensive. The issue with alternator failure is if you don't have the patience to find a good price, many people just suck up the inflated price when the mechanic gives you the bad news and you just want it fixed fast.

 

I found a good alternator/starter repair shop in my general neck of the woods. He can usually refurbish any Denso alternator to better-than-new condition for around $120. If and when the alternator in my wife's 2015 RX350 fails, I will take it to him. He did a great job refurbishing my wife's 2006 Jaguar XK8's alternator back in July 2018 utilizing the proper Denso kit with all Denso parts.

 

If you don't have to replace the bearings [you may need a press]. brushes and diode pack are very easy to swap. No soldering required. I think 3rd gen has a tensioner, so very hard to mess up the bearings.

Salim

 

FWIW my gf has a 2004 RX330. About 6 months ago the original alternator died and we replaced it with a remanufactured unit. The vehicle had about 175K before the failure so, not too bad.considering the years and miles behind what has been a very reliable vehicle.

 

Just for information .. did you experience and battery issue or any other electrical issue before the alternator went out and did the mechanic run a bench test to determine what was wrong with the alternator.

Salim

 

A bench test was performed and we were told the alternator was bad. Prior to the replacement, the battery, which was virtually brand new was not recharging.

 

To your question about mileage...I would not be as nearly worried about mileage as much as proof of maintenance. We bought a 2010 used from the Lexus dealership with all the maintenance records. Finding one that has been well taken care of will be ideal....that should be apparent from how the interior has been maintained as well any service records. We have over 185,000 miles on ours (my wife drives it) and it runs just as good if not better than some brand new cars. Good luck on your search!

 

i think if you are buying a car that is newer but with high miles (5 years old or less). Let say <100k miles. Really what maintenance is needed? It usually is oil change since Lexus are well built not too much maintenance is needed. After 100k miles you will need other fluids like transmission etc...