Dave it relates to warm, moist, air inside the instrument and the glass being colder. The mist (in effect dew) then forms on the glass. It is exactly the same as taking a cold beer bottle out of the fridge and into the warmer air. The moisture in the air condenses on the beer bottle.

Turning the lights on only warms the air inside the instrument faster than the warmth generated by the electronics alone. The only real solution is to bring the glass up to the same temperature as the warm moist air inside the instrument as soon as possible. A hermetically sealed instrument with dry air inside would also be an answer.

On the Morgans the bulbs in the instrument are incandescent and therefore generate heat. LEDs are not dimmable without complex circuitry.

A hypothetical solution that has been discussed is running warm air in tubes from the heater system. If an aircon is fitted it would work even better as the aircon unit effectively de-humidifies the air.

Peter

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