Here's the reply I received back in 2011 from the manufacturer - Caerbont Automotive Instruments
http://www.caigauge.com/ (no connection). May be helpful
Hi Nick
Misting in instruments is one of our bug bears with the older design instruments, several things have been tried over the years including sachets of silicon to absorb moisture , coatings that are applied to the inside of the glass and several other ideas, the base problem is that the gauge is not sealed and if it were it would have to be sealed with air of zero humidity inside, with air of the humidity that occurs this time of year inside when the gauge is activated through the movements and the illumination, heat is created, the air inside then condenses against the cooler walls of the instrument, either the case or the glass, because glass takes longer to heat than the case because of its thermal conductivity the problem usually exhibits itself there.
We have cured the problems over the years by using instrument movements that do not generate heat ie using stepper motors and LED illumination, the current 3 in 1 is of an older design, we are working on a design to change this and will take the design to Morgan shortly.
Hope this is of some comfort
Best regards
Gavin Roberts
MANAGING DIRECTOR
