Did Seeed ever provide a useful answer to this problem? I also get the same readings for the Grove Sun sensor at near darkness levels. It makes this sensor useless for the student FarmBeats projects. In addition Seeed replaced version 1 of the Grove Sun Sensor with Version 2. It uses a different chip based on the SI1151 and not the Si1145. The Arduino software library demos no longer work and you can not replace the Version 1 sensors in Farmbeats kits with Version 2. New software code is required yet when you order Si1145 based sensors from Seeed they now supply you with Si1151 chips. Looking up the Si website for Si1151 it does not look like it supports uv detection. Did Seeed get this wrong?