To check the power supply of the clock, locate the electrical connector and find the pin on it which supplies the power (12v) to the clock.

Take a small bulb and socket and bridge a wire from the 12v pin supplied from the electrical connector, to one of the two wires on the bulb and socket.

Next find a ground supply nearby ( the best place would be the key hole) and bridge another wire from it to the second available wire on the bulb and socket.

If the bulb lights up, it means your clock has power.