HDC2460 Status LED overheat - no connection

Hello...

i use a HDC2460 for a mobile robot. The robots software is ROS. The comunication between motor controller and the PC happens by RS232.
The controller powers 2 motors and 2 step encoders are connected.

My problem is that my PC (ROS) send commands for moving, but robot doesn't move. Afterwards i try to connect to the motor controller by Roborun+ via RS232 and USB, but this doesn't work. I dont get a connection.

The motor controllers power LED lights green, but the status LED flash with an overheat pattern. USB LED doesn't flash.
Now I ask for help...

Best regards
Georg Supper