Rs21 ff icing up again

Hi chaps

Purchased and fitted the service kit as my FF was icing up and causing noisy fan etc.
All was well for about 6 weeks when it did it again, so took it apart and defrosted the lot and put it back together again.

Have had to do this another 3 times in the last 10 weeks, so I checked all the items for continuity and found the defrost sensor giving a reading of 7.62k at 0 degrees C, whereas as all the others were as posted in the site diagnostic page.

Is this sensor a dud, and is it likely that it is the reason for the icing up. It seems appropriate given that the ice builds up mostly around where this sensor is attached (as per fitting instructions and photo) which then leads to this side of the fan icing up too,

Hope someone can help

Regards

Paul