on your radio harness there are two wires that supply +12v. One wire gives 12 volts when the ignition is set to accessory or ignition. The other is 12 volt constant which gives power even when the car is off. Both these wires run to fuse panels which are fused by different fuses. Check all the fuses that are relvant and replace as neccessary. This should turn up a blown fuse and once replaced your cars clock should hold its time. If your fuses are fine or after replacing the fuse it keeps blowing, check your wiring behind your radio. Make sure the 12 volt constant wire out of the radio is goin to the 12 volt constant wire out of car. Hope this helps.