Probable subunit of the chloroplast NAD(P)H dehydrogenase (NDH) complex of the photosynthetic electron transport chain. Required for both formation and activity of NDH. May function in assembly or stabilization of the NDH complex. Impaired chloroplastic NAD(P)H dehydrogenase (NDH) activity, probably due to a reduced stability of the NDH complex. CRR3 is not conserved in cyanobacteria and seems to be a subunit of the NDH complex which is specific to the chloroplast.