Question: Why is the Pischey Teshuva (Yoreh Deah 289:1) unsure if you have to say a blessing if you take off your mezuzah to check it having in mind to put it back on but if you take off your Tallis or tefillin within mind to put it back on you don’t have to say another blessing?
A. You could answer that it’s possible one might not think he’s putting the mezuzah back on if when checking it, it’s found unkosher. But besides that there is another reason to be in doubt, based on where the mitzvah is done which even if he took it down for some other reason like repairing the door and would put it right back onto the doorpost, still there would be a doubt whether you still need to make another blessing.
A2. Tefillin and Tallis are put onto one’s body so the need of the blessing is based on what the person has in mind so if he plans on putting it back on no other blessing is needed but the mezuzah is put onto the door of the house so it is as if there is nothing to have the mezuzah in mind when being put back on so it’s possible to say that you always need a blessing when putting the mezuzah on the door post in whatever circumstance. Or you can say that the mezuzah belongs to the person and the person is in charge of the mitzvah so if he has in mind to put it back up he does not need to make a new blessing and that is the doubt.