No. "Synderesis" is not a power but a habit because various acts can belong to one power.
Synderesis non est potentia, sed habitus quia diversi actus possunt esse unius potentiae.
Now the first speculative principles bestowed on us by nature do not belong to a special power, but to a special habit, which is called "the understanding of principles," as the Philosopher explains (Ethic. vi, 6). Wherefore the first practical principles, bestowed on us by nature, do not belong to a special power, but to a special natural habit, which we call "synderesis".
Prima autem principia speculabilium nobis naturaliter indita, non pertinent ad aliquam specialem potentiam, sed ad quendam specialem habitum, qui dicitur "intellectus principiorum", ut patet in VI Ethic. Unde et principia operabilium nobis naturaliter indita, non pertinent ad specialem potentiam, sed ad specialem habitum naturalem, quem dicimus synderesim.
Whence "synderesis" is said to incite to good, and to murmur at evil, inasmuch as through first principles we proceed to discover, and judge of what we have discovered. It is therefore clear that "synderesis" is not a power, but a natural habit.
Unde et synderesis dicitur instigare ad bonum, et murmurare de malo, inquantum per prima principia procedimus ad inveniendum, et iudicamus inventa. Patet ergo quod synderesis non est potentia, sed habitus naturalis.
As we have said above (Q79, A8), man's act of reasoning, since it is a kind of movement, proceeds from the understanding of certain things -- namely, those which are naturally known without any investigation on the part of reason, as from an immovable principle -- and ends also at the understanding, inasmuch as by means of those principles naturally known, we judge of those things which we have discovered by reasoning.
Sicut supra dictum est, ratiocinatio hominis, cum sit quidam motus, ab intellectu progreditur aliquorum -- scilicet naturaliter notorum absque investigatione rationis, sicut a quodam principio immobili -- et ad intellectum etiam terminatur, inquantum iudicamus per principia per se naturaliter nota, de his quae ratiocinando invenimus.
Now it is clear that, as the speculative reason argues about speculative things, so that practical reason argues about practical things. Therefore we must have, bestowed on us by nature, not only speculative principles, but also practical principles.
Constat autem quod, sicut ratio speculativa ratiocinatur de speculativis, ita ratio practica ratiocinatur de operabilibus. Oportet igitur naturaliter nobis esse indita, sicut principia speculabilium, ita et principia operabilium.
According to the Philosopher (Metaph. viii, 2), "rational powers regard opposite things." But "synderesis" does not regard opposites, but inclines to good only. Therefore "synderesis" is not a power. For if it were a power it would be a rational power, since it is not found in brute animals.
"Potentiae rationales se habent ad opposita", secundum philosophum. Synderesis autem non se habet ad opposita, sed ad bonum tantum inclinat. Ergo synderesis non est potentia. Si enim esset potentia, oporteret quod esset rationalis potentia, non enim invenitur in brutis.
Further, Augustine says (De Lib. Arb. ii, 10) that in the natural power of judgment there are certain "rules and seeds of virtue, both true and unchangeable."
Praeterea, Augustinus dicit, in libro de libero arbitrio, quod in naturali iudicatorio adsunt quaedam "regulae et semina virtutum et vera et incommutabilia".
Those unchangeable notions are the first practical principles, concerning which no one errs; and they are attributed to reason as to a power, and to "synderesis" as to a habit. Wherefore we judge naturally both by our reason and by "synderesis".
Huiusmodi incommutabiles rationes sunt prima principia operabilium, circa quae non contingit errare; et attribuuntur rationi sicut potentiae, et synderesi sicut habitui. Unde et utroque, scilicet ratione et synderesi, naturaliter iudicamus.