It has been generally believed that Harsiese A was a High Priest of Amun(HPA) before he became a king at Thebes. However, Karl Jansen-Winkeln, in a JEA 81(1995) pp.129-49 article, has demonstrated that all the Monuments of the first Harsiese show that he was never a High Priest of Amun--albeit the son of King Sheshonq II. Instead, Harsiese A was a King at Thebes in Osorkon II's first decade of rule and is different from the High Priest Harsiese.
It is the second Harsiese, the High Priest Harsiese B, who is attested as a High Priest of Amun under Osorkon II in statue CGC 42225. However, this statue was dedicated by the Letter Writer to Pharoah Hor IX, who is attested on the walls of Temple J at Karnak which was built in the final years of Osorkon II's reign. Hor IX is later known to have served under Pedubast I and Usermaatre Meryamun Shoshenq VI--under whom his funerary cones were inscribed(see D. Aston, JEA 75(1989) p.152). Hence, the High Priest Harsiese here can only be Harsiese B. Harsiese B served in office as the High Priest of Amun for almost 3 decades under Osorkon II(final 3 Years), Shoshenq III(first 7-8 Yrs) and Pedubast I(18-19 Years). He presumably replaced the High Priest Takelot F at Karnak when the latter proclaimed himself as king Takelot II. He is last attested in Year 19 of Pedubast I as Nile Quay Text No.27 shows.
