Hi,
I know this is a slightly old topic but just in case you (or anyone else) is still having this problem...
We had the same problem on my wife's K13. There is a cable that runs from the temperature control knob to the air mix door control linkage. It operates similar to how a bicycle brake cable works, i.e. outer sheath/casing with an inner cable that runs through the middle. I our case the outer casing had become detached from it's mounting point at one end, meaning it moved when the knob was turned instead of the inner cable being moved.
The fix was simply a case of slotting the outer sheath back in to it's holder. Unfortunately, I didn't take any pics at the time I fixed it.
However, have a look in the workshop manual (http://manytodo.com/downloads/Micra K13/Nissan Micra K13 Workshop Manual.pdf) in section HAC-149 to HAC-150, it gives details of how to check the air mix control cable. Although it mentions removing the Foot Duct, I found this wasn't needed in our case. I was able to access the cable fine by removing the A/C cluser lid and Audio unit (see Workshop manual: IP-16, steps 10 & 11).
If you still have the problem and are struggling with following the less than clear pictures in the manual, let me know and I'll see if I can pop the covers off and get you some pics.
Regards,
Dave
