Press and hold the volume knob for at least twenty seconds and see if that turns it back on. If that does not get the radio working again then the last thing to check are the wires on the back of it, if they are loose or damaged it may make the stereo fail as well. Radio problems on the 2011 ford fiesta can be caused by a blown fuse or damaged ^{3. Insufficient Coolant. If your coolant level is low, there is a chance it is pushing air into the cooling system, and the coolant temperature sensor will not read the coolant temperature correctly. If the coolant level is low, you need to top up the coolant reservoir.} hwb4u.