The blessing on ripe carobs is Haeitz. The blessing on carobs that are small, and have not yet ripened to the point of chain like wrinkles, is Hadama. If however, the carbos are bitter and are not fit to be eaten at all then no blessing is said over them, even if they are ripe.
Shehechiyanu: The blessing of Shehechiyanu is not recited over carob being it is not a fruit that people normally anymore.
Insects: Carobs tend to be infested with worms and insects and hence must be checked thoroughly prior to eating.
 Luach of Rav Prus; Luach of Rav Elyashvili; See Admur 202/3-4; Seder 6/1; Michaber 202/2
 Admur 202/3; Seder 6/1; Rama 202/2; Ketzos Hashulchan 49/10
The reason: As they are not yet considered a fruit. [Admur ibid]
 Ketzos Hashulchan 49/10 footnote 16; See Admur ibid, Kuntrus Achron 202/2; Michaber 202/2
 Piskeiy Teshuvos 225/17 footnote 123 based on Kitzur SHU”A 59/17 that we do not bless Shehehciyanu on foods that do not contain Simcha.
Regarding the matter of reciting Shehecheyanu on carob, please see below for the opinion of the Lubavitcher Rebbe:
From a note of Rabbi C.M.I. Hodakov, dated the eve of the 15th of Shevat, 5718, Brooklyn, NY
I asked the Rebbe if Shehecheyanu should be made on Bokser (carob), and the Rebbe answered that in Russia they would make the Brocho Shehecheyanu on carob.