  We derive closed expressions for the universal weak localization peak of the
average conductance peak heights in Coulomb blockade quantum dots in the
crossover from orthogonal to unitary symmetry. The scale for the crossover is
independent of the number of channels in each lead, in contrast with the case
of open dots. The functional form of the weak localization peak is independent
of temperature. We also derive analytically the variance of the conductance
peak heights as a function of the crossover parameter.
