[John Pancoast]

Iirc and game play suggests such, enemy ships and planes don't use their radar to locate u-boats; their radar in the game only serves to warn the player of their prescence.
Even such radar equipped units rely only on visible sighting. I.e., the times when you run into a convoy with radar equipped escorts, that is why they never come after you until they see you and you see them.

A standard radar equipped escort's tactic once a u-boat showed on the radar (i.e. when it wasn't visible to the eye) was to run down the bearing guns ablazing and drop depth charges on the swirl if applicable. Unfortunately per above this is not done in the game via radar which is a shame as AOD modeled it well.

I know of no mod that simulates this very common s.o.p. Anyone else know of one ?
It is beyond my skills to make one.