Check the fuses. Cigarette lighters have overheating safeguards built in that will cause the sockets to short and blow the fuse for protection. Very often cell phone chargers and other devices have contacts on the plugs that bridge those safety devices and cause the fuse to blow if they are plugged in just right. They use power outlets now to prevent that from happening. If the fuse is blown, replace it, then watch how you insert the GPS plug. Always be sure to insert it the same way that doesn't cause the fuse to blow.