The cause is simple to understand. When the air inside the instruments becomes warm any humidity in the air condenses on the cold glass face of the instrument. It is exactly the same effect as the misting on the inside of the windscreen, or condensation on the outside of a cold bottle
It is probably very rare in closed sedans where the temperature is more uniform due to running the heater. It is also very rare on bikes. I have seen it on older bikes, and sometimes occurs if a bike is parked in the sun and there is moisture inside the instruments, perhaps because the transparent glass remains at air temperature but the inside parts of the instrument are warmed. I once had a watch that did it too.
Understanding the problem is one thing. Knowing how to stop it is another. The problem is well known and one must ask why, after all this time, the makers of the instruments for Morgan have not produces sealed instruments. I generally drive with the lights on and someone has suggested that more modern instruments with LED lighting would be less prone to the problem. The idea is that LEDs produce less heat to warm the air on the inside of the instrument.
Has anyone tried fitting LEDs?
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