Check the schematic--a few vehicles switch from the ground side of the fan motor, not the high side. If so, there should be 12 volts to the motor full-time, regardless of the switch position, and you'll need to check voltage on the ground side. If you have no juice to the motor, it's time to find out why.heck the schematic--a few vehicles switch from the ground side of the fan motor, not the high side. If so, there should be 12 volts to the motor full-time, regardless of the switch position, and you'll need to check voltage on the ground side. If you have no juice to the motor, it's time to find out why.