If you're looking to disable a rental car's GPS, there are a few different ways you can go about it. The first and most obvious way is to simply unplug the device from the power source. This will render the GPS inoperable until it is plugged back in. Another way to disable a rental car GPS is to remove the fuse that powers the device. This can usually be found in the vehicle's fuse box, and once removed, will again prevent the GPS from working until the fuse is replaced. Finally, some newer vehicles have built-in GPS units that cannot be disabled without affecting other functions of the car. In this case, your best bet is to contact the rental company and see if they can provide you with a temporary override code or switch that will allow you to disable the GPS while still allowing you to use other features of the vehicle.