there are many reasons or causes for grounded electrical system.. the hard part is how to locate and isolate it, it entails a very tedious process unless you are familiar with your car's wirings...as such, i would suggest to seek professional aid .. my cent...

but if you can describe more or at least narrow down the possibilities (for us to make an intelligent diagnosis if not wild guess), it would be better. we will try to help you as much as we can... regards..