It is recommended to clean the communication cable between the Hand Unit and the Control unit inlet and outlet holes once a week. If you have a Dual configuration system, clean the cable between the Primary and Secondary control unit as well.
In addition, if you are receiving either the 'HU comm error' or 'Primary / Secondary comm error' multiple times, we also recommend cleaning the holes.
Disconnect the communication cable from the Hand Unit and the Control Unit or from both the Primary and Secondary Control Units.
Dip a small brush in Ethonal and brush the inlet and outlet holes.
Watch the video for instructions: