Guiding of highly charged ions (HCI) through tilted capillaries promises to develop into a tool to efficiently collimate and focus low-energy ion beams to sub-micrometer size. One control parameter to optimize guiding is the residual electrical conductivity of the insulating material. Its strong (nearly exponential) temperature dependence is the key to transmission control and can be used to suppress transmission instabilities arising from large flux fluctuations of incident ions which otherwise would lead to Coulomb blocking of the capillary. We demonstrate the strong dependence of transmission of Ar$^{9+}$ ions through a single macroscopic glass capillary on temperature and ion flux. Results in the regime of dynamical equilibrium can be described by balance equations in the linear-response regime.