http://www.uboatarchive.net/Design/D...iesTypeIXC.htm
Finally found a good reference. As to this US-study from the type IXC 1945 it is as followed:
No meter (also the receivers in the enginge rooms) had illumination, except the dials for Rudder, Planes, Machinetelegraph and the TDC in the Conning Tower and Bridge. All instruments where coated with long life flourescent radium color.
No info on the meters from the electric engine. But i think they had illumination.