When we receive this phone call at Rawal Devices, 98% of the time this is caused by a leak in the system or the system having a low charge. We recommend isolating the APR Control by closing all of the ball valves, and diagnosing the system per manufacturer’s recommendations.
The other possibility is that the evaporator is in a constant low load condition where modulation is needed. For example, low airflow (below 375 cfm/ton), dirty filters, loose belt, extremely low room setpoint (below 68 deg), high percentage outdoor air during low ambient conditions, etc. In these conditions it is beneficial for the APR Control to operate to prevent floodback and icing.