I would really suggest to remove the radar alltogether, since the mechanical unreliability is not there in SH4. It gives a totally unrealistic advantage to late war careers.
I've read a lot of books about the submarine war, and the only time I've read about a working radar that was actually used was about a hohentwiel set installed in U 234 on its abortive japan voyage. That was May 1945.
A whole lot of people didn't even know that radar for submarines was available!
I know U 995 carries Hohentwiel as well, but keep in mind that the present condition is not historic.
U 995 was just under refit into a snorkel boat when the war ended but made all its patrols without Snorkel and without Radar.
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