What happens if you take off your mezuzah because its not yours is a bracha required if you change mezuzas?
The Sefer Kvias Mezuza KiHilchato (Ch 12:15, pg 176) says:
"If you take down a Mezuza to switch it with another, some say that you have to make a Bracha.
In the footnotes he brings Rav Moshe Feinstein (in Oholei Yeshurun, Vol 2, laws of Mezuza, footnote 261) who says explicitly that you do not make a Bracha. He brings the Mishna Berura - in related Halachot - who implies that one should make another Bracha.
He concludes that - as with any other Bracha-in-doubt - that one should not make a Bracha when switching Mezuzot.