On Friday I left work shortly before 5 PM and checked my Dexcom. It turned on showing... static. Nothing but a black gray and white array of dots. Be still my heart! I tried again and it said: Out of Range for 4:53:06. Waited a minute and tried it again: Out of Range for 19:35:34.
OK, called Dexcom. After being on hold a while, a customer service tech (named Matthew) called back while I was on the bus. While on the phone with him, the Dexcom changed to say Error HWRF Call Tech Support. He told me in that case I should press the restart button with a paper clip. I got home and pressed the restart button and it started up, but asked me to input the time and date, and showed no bg history on the graph. He said that's not what it's supposed to do, and that they'd send me a new Dexcom. He also said the FDA required them to ask my weight, and that if there was water damage (which he didn't suspect) that there'd be a $199 charge.
I was going to use the other Dexcom G4 (which still works) but the sensor failed and so I yanked it and gave up the ghost.
Saturday I tested my bg 6 times and it ranged from 79 to 106; WOW!
Then Sunday my bg meter gave errors for four strips in a row. I thought it was broken, but a few hours later it worked again (I was 186).
I don't know what was up.