The ARS-USB includes a functionality that when it detects that one of the limits (CCW or CW) has been reached, the relay that allows rotation in that direction is DISABLED (See Note1)
In other words, if the feedback voltage readout in an Azimuth rotator is 0V or equal to the limit value of CCW, the relay allowing the clockwise rotation (left) is disabled. In a similar way if the reading feedback voltage is higher or equal to the programmed Stop for CW / right value, the relay allowing the CW / Right turn is disabled.
Of course you can disabled this feature, so power on the ARS-USB in “Absolute Mode“. This mode is activated pressing “F2” button and power ON the unit.
So remember you can disabled the end limits detection for testing purpose, in “Absolute Mode”.
Note 1: It’s the same in Elevation, If the ARS-USB detects the rotor is at the Upper limit, the UP relay will be disabled. And the same when the rotor is at the Low limit with the Down relay.