Comfort led's on most are low viz during daylight hours or strong sunlight.
Check of an evening when it's a little darker.
We not know the make of the sounder you have up there, but i can say that the tex oddy's led's are very poor viz during daylight hours.
Common fault for lack of comforts are the module/battery especially if the sounder tests ok or if one discovers it to be a decoy (dummy).
e manno, May 2013