Once dried out the only way a clock will continually fog is if the rubber seals under the glass and crimp ring are not doing their job. Pull the idiot light holders out and dry the clock thoroughly. Refit the rubber bulb holders and they should be fine. If they fog again after rain etc i suspect the seals.
You can see here if the rubber bungs are in these four holes the unit should be pretty well rain and condensation proof but it needs to be dry in the first place
Not taking sides here just trying to offer a solution :