my Tach just stopped working ! help !

OK, I have a 98 Aurora, recently had the transmission rebuilt. I was driving home in a heavy rain a couple days later and my tachometer just went dead, nothing, no movement at all. I took it back to the shop thinking the tranny pull may have contributed or was related, but they looked at it and told me the tach sending unit was working properly and I most likely blew a fuse or something. Other then this the car runs and drives perfect (for an olds...LOL). Is there a fuse for the tach or does anyone know how the tach is wired into the fusable circuit.

I will check my grounds and go from there, any other ideas?

Thanks for the help !