Check menu C03 of Metacentre system controller for accurate configuration (I-485, V-485, iPCB) For I-485 or V-485, ensure the respective compressor controller is in the 'started' state. Note: this can be either the compressor controller itself, or a Metacentre device located between the compressor and the Metacentre system controller. For example, Metacentre VSD Ma. Check the remote load parameter and address ID at the compressor controller or device located between the compressor and the Metacentre system controller is configured correctly. The address ID for any compressor should be unique and match the address ID at the Metacentre system controller. Check RS485 wiring & polarity For iPCB, ensure the respective compressor controller is in the 'started' state. Ensure LED 4 'Ready' of the iPCB is illuminated. If not, check voltage continuity between iPCB PIN C04 and 'READY' voltage source from compressor. If LED 4 'Ready' is illuminated, check voltage continuity between iPCB CO3 and the terminal PCB of the Metacentre system controller Check fuse FH5 of the XPM-TAC24 inside the Metacentre system controller.