An agricultural baler includes a main bale chamber, needles, knotters, a triggering system, a knotter lock, a blow-off mechanism, and a monitoring system. The needles are coupled to the main bale chamber and thread twine around a formed bale. The knotters receive the twine from the needles and tie the twine. The triggering system is for activating the needles and the knotters. The knotter lock is a manual lock of the triggering system thereby preventing the needles and the knotters from being triggered. The blow-off mechanism directs a flow of air at the knotters and the needles. The monitoring system has a single sensor that provides signals indicating a normal operation of the knotters, and whether the knotter lock is engaged.
