What it means
Communication through Port C or Port E between the controller and user-interface path has failed.
This entry is tied to the exact STS message family documented by Sullair. The same words can mean something different on another controller generation, so confirm the displayed message and machine documentation before acting.
Likely causes
- Cable or connection fault between the controller and user-interface panel
Operator-safe first checks
- Record whether the message names Port C or Port E.
- Note whether the fault appeared after maintenance or cable movement.
Trained maintenance / service checks
- Inspect the relevant cable and connectors.
- Check continuity/connection quality using the STS wiring information and lockout/tagout as required.
Reset or keep running?
Do not use repeated resets as a substitute for diagnosis. If the condition involves electrical power, a motor overload, high pressure, loss of cooling, abnormal temperature, or a safety circuit, correct the underlying problem before returning the compressor to service.
Source confidence
OEM VERIFIED
This message and its troubleshooting direction are traced to the Sullair STS controller troubleshooting guide.
Source: Sullair STS Controller User Manual, part 02250241-178 R01. Referenced manual page: 33.