I posted two years ago about my 830 altimeter going haywire after a few drops of moisture fell on it; the first time rain, the second time sweat. I would get readings like a -13 grade when I'm going up hill. Or a elevation total like I climbed Mt. Everest. I tried the hair blower, no luck. I was told $95 to replace it, despite being a manufacturing flaw; no thanks. So, I removed grade and elevation from my screen and, instead, did the correction in Garmin Connect. Now, the fix, just wait. Yup, two years later, it started working again. Don't recall doing any Garmin Express updates, so, unless it came through the iPhone app, it wasn't a software update. It must take a very, very long time to dry. Strange...