I had the same problem. When it rained it the water came right in on the on-star mic. Alot of people said it was probably the drain but that was not the case. The center lamp gasket was no good so i just siliconed around it. That roof light just pops off, i then put a small bead of silicone around the bottom of the light and some in the hole where the wire goes into the headliner. After months of putting a plastic garbage bag over my kenwood radio I finally fixed it.