I recently replaced my alternator because it had a bad bearing and also the battery light came on. After I replaced the alternator with one I purchased at the auto parts store, The red battery light was still on (but the bearing buzz went away)

Thinking it was the alternator, I checked the voltage and it was indicating 14V. I took it back to the auto parts store and they hooked their little handheld computer to the battery terminals and let it run its checks. The guy said the alternator was working and that my battery checked out OK also.

In addition to the battery light, if I don't put it on the trickle charger overnight, on my short drive to work (less than a mile) the LR3 exhibits the crazy screen syndrome where all the displays start to flash off and on. Also, and this happens all the time, the LR3 shifts late and it idles at around 1300 RPM instead of the 750 or so that it normally does. I checked the battery voltage in the morning and it's been down as low as 12.2 volts (with the truck not running)

Also, when I first start the truck, there's no red battery light for about 10 seconds.

I called my local LR mechanic to make an appointment to bring it in but he said the alternator I installed was probably the problem. He said that he's seen it before and that I needed to install a Denso instead of whatever the brand was that I purchased.

So question, is there any other thing I can diagnose before I purchase another alternator? I really don't understand what's happening... What are your thoughts on installing a Denso alternator?

 

I had a similar problem that had different symptoms. My '06 came with a "new" remanufactured alternator but it had a P0561 code that didn't throw a CEL or the battery light. The code indicates "unstable" voltage. At any given time it would show 13.8 -14.2v, so that seemed OK, but it was apparently fluctuating outside the allowed range. I didn't have the dash disco. A warranty replacement solved it. I assume it was the regulator.

Guess my point is that you should see if there's a code, because even if it's testing with high enough voltage there could be something that the finicky LR3 doesn't like. But yeah, it's probably the alternator. New Denso would probably solve it, but I think they're $500...and not returnable if it doesn't solve your issue.

 

I’d start by looking if you have a parasitic drain. Lots of YouTube videos.


Can be done with a multimeter but a clamp meter makes it easier IMO on a LR3.

Could be the alternator causing a drain while the car is off but it could be anything. If you find you have a parasitic drain, next step is to pull fuses to find out where.