2009 Lexus LS460 Alternator Problem?

Mile_High_Flyer · October 18

Usually my self installed volt meter shows the car running at 14.3 Volts all the time. However, yesterday I noticed it showing 12.5 volts. A short while later, it went back to 14.9 Volts for a short time. Then went back to 12.6/12.5. Did this a few times. I haven't been out today yet. I assume it's a faulty alternator, but no CEL or anything showing on dash. Drive belt appears to be correct tension.

If it is faulty, how big a job is it to replace? Looks as if it wouldn't be the easiest of access. Plus I'd have to find an alternator.

Any comments would be appreciated, thanks.

Malc1 · October 19

Ls460 alternators seem readily available on-line to purchase at a snip at a few £00 or so …….. big expensive cars of course ……. did you watch the video on a concurrent post about why NOT TO BUY the 460 🤔

Quite sad for you tbh so hope you find the root cause of the issue before you actually buy that replacement alternator ……. probably a biggish job to change it whatever

Someone will come to your aid soon with specific useful thoughts I’m sure 🤞🤞🤞

Good luck

Malc

Herbie · October 19

Sounds like the belt may need tightened up (although I appreciate that you say it seems to be alright) or it may need new brushes.

Replacing the brushes is usually a very easy DIY job once the alternator is out of the car.

donkmeister · October 19

First thing to rule out is the volt meter... Is it plugged in to the cigar lighter, or have you tapped off somewhere? Or are you getting the voltage via OBD?

Far be it from me to cast aspersions at another man's wiring, however I've seen enough dodgy crimps that my first thought is "the car isn't complaining - has he just got a loose wire to the volt meter, or possibly is the volt meter dodgy?" Either way, better to rule it out before loading up the parts cannon.

Mile_High_Flyer · October 21

Hi guys. Thanks for the replies. Hooked into the driver's fuse box. Right hand drive. Wondering today if it might be the regulator, as opposed to the actual alternator, although I assume the regulator is built into the alternator instead of being separate. It takes a while before it starts playing up, presumably after it is well warmed up. It has been okay until a couple of days ago. I believe the volt meter is okay as I would expect it to go to zero, rather than to Battery voltage when it is faulting, but I will be checking that . I will also be checking directly across the Battery in a couple of days or so, but I don't expect it to be any different, although one can but hope!

Is it easy enough to replace the brushes? I have done so previously on other cars, but not sure about these. If the belt was loose, I would expect it to squeal as it slips, but no noise. Haven't run it at night yet since the problem surfaced.

Malc, I am aware the 460 has problems, but I got it a very good price, so am hoping. That's why I've kept my LS430! Lol.

G1974 · October 21

Hello, from owning and driving many cars over the last 50 years your voltage readings would seem to be CORRECT to me for modern cars using AGM batteries, the variation in readings that you see are likely due to the varying state of charge of the Battery i.e. 14.3 v = on charge 13.5 v = float charge 12.5 v = off charge, I have seen just these reading on the 12 volt system on VW Passat / Golf and now my NX350H. If the car has a fault it will tell you.

Mile_High_Flyer · October 27

To take the alternator off, do you drop it down through the bottom, or pull it up through the top? A quick look from the top, looks as if there is more room to drop it down.
Does anybody know if there are instructions anywhere on how to go about removing it?

It seems that driving at night, it may not be a problem, but only done so twice, so can't be sure. I don't know if it may be because it is cooler, or because there is more load on the alternator with the lights on.