I purchased my Highlander used and the next day noticed that the heater only heated up when it felt like it or after I hit a bump. Well I live in Northern Michigan where going without heat in your car is not a possibility. After lots of research online about the issue, I had figured out that there was a short in the wires back behind the dash. My brother ended up taking it apart and soldering (sp?) the wires back into the part. My apologies as I can't recall the name of the part. Well about a year later, the same thing happened again. To which my brother tore it apart again, and added more wire to it so that there was some extra. Simple easy fix and much cheaper than the $700-1500 I have seen posted for possible fixes.