'08 150 SCREW. I had the common problem where the heat was either full hot or full cold, nothing in between. Replaced the actuator and it seemed to be good. A few weeks or months later, the actuator started chattering on startup, like it was stripping its gears. Lifetime warranty, replaced it again... and the second new actuator does exactly the same thing. (I am 100% certain I did not remove and replace the same one.)

So other than a third failed actuator, what else could the problem be?