'NO COMMS' is displayed in the AC unit Status- possible CEXT issue

If you are seeing the No Comms error on the iZone Wall control panel and there are more than 8 zones in the design, CEXT could be the reason for that error as well. 

You can check the following in order to rectify the issue.

Check if there is missing or no communication

You can check if there is any issue with the CEXT which can be causing Communication issue between the AC Unit Module and CPU as this part is attached in between the CPU (C225) and AC Unit Module (C325).

Check for any damaged Pins

Check if there are any damaged pins on the extension module or damaged connection points where unit module C325 connects to the extension module

Replace the zone extender - CEXT

Once you confirm from the above checks that the issue is related to the CEXT, we would recommend you to replace the CEXT and that should resolve the no Comms issue caused by it.