1992 Oldsmobile Ciera Fan Motor Connection

I have a 1992 Cutlass Ciera that I brought 6 months ago and my fan motor burnt out. I replaced the motor and it still didnt work. I cut the main wire that runs to the fan in front of the engine. I ran a 12 gauage wire (postive and negative) from the fan to the battery. Then a postive and negative from the battery to a toogle switch but keeps burning out after the car is drove about 10 mins. I need to know were the ground connection is and how to propertly wire a toogle switch from the main blower fan. Will take any other other suggestions on fixing the problem.