My 2015 ST just started the broken gear tooth popping noise yesterday. I spent several hours last night and this morning researching the problem which brought me to this thread. I haven't read all (currently) 24 pages but I have noticed here and elsewhere that there seems to be a lot of discussion about part numbers and slight differences between the part removed and the part installed. Too, there is a lot of discussion about almost immediate failure of the new part.
My car has 45K miles on it so a warranty repair is not possible. I know from the amount of work to get to the defective part that hiring someone to do it will cost north of $200. I cannot justify spending that kind of money even once, let alone repeatedly. I will have to do it. Being old and fat, I have no desire to do this more than once. I will continue my research. This is what I know now.
There are actually three blend door actuators on the Fiesta. See the diagram on this page:
http://www.tascaparts.com/oe-ford/be8z19e616b
Items 19, 20, and 21 are all blend door actuators and all are very similar but slightly different:
19E616C
(YH-1896)
HVAC Blend Door Motor
With Automatic Air Conditioning Manual Air Conditioning ; Mode Control
Item 21 on the Tasco diagram
19E616B
(YH-2016)
HVAC Blend Door Motor
With Automatic Air Conditioning Manual Air Conditioning ; Temperature Blend Door
Item 20 on the Tasco diagram
19E616A
(YH-1895)
HVAC Blend Door Motor
With Automatic Air Conditioning Manual Air Conditioning ; Inlet Door
Item 19 on the Tasco diagram
As I say, I have not finished my research yet. I have to go to work now so I won't be able to continue until tonight. But what is obvious to me is that a lot of people are ordering parts that might or might not be what they need.
If this information has already been provided in the dozen or so pages I haven't read, just spank me and send me home.