360 No AC temp control

I installed a new compressor and dryer a couple of years ago . Still blows icy cold, however only in “LO” , I.e. the system is always on .
Common sense points to a fault in the temperature selector or the cabin temperature sensor. Could be something else as well I suppose.
My question is simply is this reoccurring common problem with our old cars and is it typically one of the above before I start buying parts?
Thanks , JC

 

Can you give a picture of your selector controls?
That will help a lot in diagnosing via internet