Yesterday my Sigma 1909 heart rate indication became unusable. Chad, one of the Sigma customer folks provided a list of possible trouble shooting fixes. Unfortunately, none of them worked. Today I e-mailed Chad and mentioned that the HR was still inop and would like to resolve the issue before I leave for a week long ride in three weeks. Chad responded that parts were on the way to me and that he was doing the same ride.
Thanks Chad and thanks Sigma!