New blend door motor still no heat?

Answer 1

This is a little difficult to answer without knowing what car model we are talking about, so I'll give you a generic answer. The blend doors in modern automobiles are under computer control...not like the old slide lever with a cable attached and you move from red to blue and back. The motor is generally activated by the computer and if there is a fault in the system, the computer goes into it's "panic routine" and will usually shut the motor down to prevent further damage since it generally doesn't understand what's happening.

Typically what's happening is that the cheap plastic blend door broke and the system can no longer drive the door to a stall position and calibrate the movement range of the door. Complete computer confusion ensues since generally a full breakage was not an event foreseen by the software engineering teams. Hardware and software guys never talk and this type of occurrence is the result.

Usually the motor is good, it's the broken blend door combined with the computer fail safe algorithm that makes it look like the motor is bad. A lot of service techs will just replace the motor since that is usually easy and has a good payback instead of trying to understand and fix the problem. HeaterTreater has engineering analysis and fixes available on their web site for the most common failure models and are expanding their product portfolio. Check heatertreater.net to see if your model is listed.