We’ve had a particularly wet winter in the Pacific Northwest this year, and I got a chance to fly my motorglider today for the first time in over a month. Just prior to takeoff I noticed that my LXNAV S7 Vario had a small spot of visible condensation on the interior of the glass. I’ve noticed this one or two times before, and it has usually been on days when you might expect condensation to form, normally disappearing within a few minutes.

Today, however, in addition to the condensation I noticed a progressive failure of the vario screen image which gradually deteriorated into diagonal lines. With the engine warmed up enough I was able to add some heat to the cabin, and over the next half hour repeated restarts of the vario allowed it to last a little bit longer each time before the screen deterioration occurred once again. After about an hour of flying I returned the motorglider to the hanger, and one last check of the vario showed it to be working properly for at least the 10 minutes I ran the final test.

I’ll have to follow this over time to see if there are any obvious patterns of malfunction, but it occurs to me that condensation within the instrument may have resulted in reversible problems with the electronics. Over the years I’ve been watching for potential corrosion issues with the airframe, but this is the first time I realized that the avionics might be affected as well.

Has anybody seen anything like this and have any advice? I can probably deal with this by placing a small heat source in the cabin since the aircraft is hangared. I’ve also had variable success with dehumidifying granules in the past.