Garmin GSC10 battery warning?

[bychosis]

I have an edge 705 and two GSC10's on different bikes. I haven't had it that long, having bought second hand. Recently one of the bikes decided not to show cadence, or was erratic in its readings. Does this mean the GSC10 battery is low? Or is there another warning for low battery? My google-fu hasn't led me anywhere meaningful. Anyone got a simple answer?

[queequeg]

you can press the little test button on the sensor and then spin the wheel and cranks. it should flash red or green with each pass of the wheel or crank magnet. if it doesn't, battery is flat. you need a CR2032 in each.

[kb]

Double check nothing has moved around too. It can sometimes be a bit fiddle optimising wheel magnet, crank magnet and stay sensor position.