my radio and clock no longer know when the ignition is switched on - could a blown fuse cause this problem ?
yes it can, and the switch itself can be faulty.
The first step in any electrical question is to check ALL the fuses in the vehicle. Use a test light with the key in the on position and see if you have power at both sides of the fuse. A fuse that is failed will have power at one side and none at the other. Do not be concerned at this time with fuses that do not have power at either, as these are circuits that are not active.
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