Hacham Ovadia Yosef, in his work Hazon Ovadia, cites a debate among the authorities as to whether one recites the Beracha of "She'he'heyanu" before performing the Misva of Bedikat Hames searching his home for Hames on the night before Erev Pesah. Bedikat Hames is a Misva that one performs only once a year, and thus it should seemingly warrant the recitation of "She'he'heyanu." Just as we recite this Beracha when performing other infrequent Misvot, it would seem, we should similarly recite "She'he'heyanu" when searching our homes for Hames. This is indeed the position taken by the Peri Hadash (commentary to the Shulhan Aruch by Rav Hizkiya Da Silva, 1659-1698).
However, the Rosh (Rabbi Asher Ben Yehiel, 1250-1327) and others maintained that one does not recite "She'he'heyanu" before performing Bedikat Hames, because this Misva is incorporated into the broader framework of the celebration of Pesah. According to this view, the Beracha of "She'he'heyanu" recited on the night of Yom Tov covers all the Misvot associated with the holiday. Thus, for example, a person does not recite "She'he'heyanu" upon completing the construction of his Sukka before Sukkot, since the "She'he'heyanu" recitation on the first night of Sukkot covers all the Misvot relevant to the festival, including the building of the Sukka. Similarly, then, one should not recite "She'he'heyanu" when searching the home for Hames, as this Misva is part of the general framework of the Pesah celebration.
As for the final Halacha, Hacham Ovadia rules (listen to audio recording for precise citation) in accordance with the Rosh's view, that "She'he'heyanu" is not recited before Bedikat Hames. Nevertheless, he recommends satisfying all opinions by preparing a new fruit before beginning the search for Hames. After beginning the search, he should look at the fruit, recite "She'he'heyanu," and then resume the search. Upon completing the Bedika, he should recite the proper Beracha over the fruit and then eat it. Alternatively, one can ensure to wear a new suit or sport jacket at the time of the Bedika, and recite "She'he'heyanu" over the new garment after he begins the search.
Hacham Ovadia emphasizes that this recommendation applies only on the level of "Midat Hasidut" an added level of piety. According to the strict Halacha, one does not recite "She'he'heyanu" and is not required to satisfy the minority view of the Peri Hadash.
Summary: One does not recite "She'he'heyanu" before performing Bedikat Hames. Nevertheless, given the difference of opinion on this matter, as an added level of piety it is preferable to arrange to have either a new fruit or new garment at the time of Bedikat Hames and recite "She'he'heyanu" over the fruit or garment.
