Curt Steven Mayes, Pronominal Referents and the Personality of the Holy Spirit (Th.M. thesis, Dallas Theological Seminary, 1980), p. 35
http://lhim.org/blog/2013/07/03/the-...sean-finnegan/
Curt Mayes helpfully explains the flow of thought in this passage:
It is necessary to begin back in verse seven. There the Spirit is introduced as the παράκλητος [advocate] and becomes the subject of an extended discussion. Αὐτόν [him] in verse seven refers back to παράκλητος, as does ἐκεῖνος [that one] in verse eight. Then verses nine through eleven explain the work of the παράκλητος (with respect to the world) which (work) was introduced in verse eight. Notice the dependency of verses nine through eleven on verse eight, as attested by the incomplete sentences in the former. Verse twelve sets the stage for another statement about the work of the παράκλητος—this time with respect to believers. Ἐκεῖνος is used in both verses thirteen and fourteen, probably with the same reference. On the basis of this sequence, then, it is this writer’s contention that ὀ παράκλητος is introduced in 16:7 as the subject of the passage and remains the subject through 16:15. Ἐκεῖνος would then refer to παράκλητος in each instance (vv. 8, 13, 14)—simple agreement, the general rule.