The blower motor is sometimes making noise. I believe it is a sign the bearings are going. I replaced it only five years ago. Is this normal? The original one lasted 14 years.

 

Roll the dice on used OEM would be my call

https://www.ebay.com/itm/313784154909

 

Isn't that a high pitched noise like an oscillation? Other than the bearing, there sometimes happen strange noise from the motor controller. It is high pitched and you even can hear it when the motor is running slow.

 

Could it be debris or a leaf stuck down there and touching the fan? Try turning the fan speed to maximum for as long as you can tolerate, to try and free-up the debris (if it's physical debris). When was the last time you changed/checked your cabin filter?

 

The noise is not high pitched. It does go away when the fan is off. I tried raising the fan speed; the noise does not get worse.

 

That's what I worried about. Toyota/Lexus had complains from owners of LS400 and some other cars. Owners were claiming that strange noise could be heard from somewhere near the blower motor. It was found to be from the blower motor controller and Toyota/Lexus changed the design of the controller as is shown below.


The left side is the one before the counter measure and the right side is the countermeasured one to be quiet. But still there were some problems. LS430s were designed not to have noise problems but still there happens some. Yours may be so. It is not very easy to eliminate the magnetostrictive vibration.