BTW don't look up lexus dealer prices. these things are pieces of junk on ebay all day long. $80 used or $150 remanned.

i'll bet under the plastic is a replaceable voltage regulator. your brushes may be worn down. anyway check it out https://www.ebay.com/itm/2014-2015-L...frcectupt=true

honestly these things look dinky. keep in mind they need good cooling so if yours are covered with leaves or blocked by debris, they'll overheat fast.

 

Any updates on the cause?

 

I replaced mine with a new battery as well still only seeing around 13.5... although No Matter What accessories I add it stays around 13.5 even with the stereo cranked up over 13 so the alternator is definitely still producing just not at 14 volts it may be set buy the factory and controlled by the ECU.