What it means
The user-interface/controller voltage monitor has detected an internal high- or low-voltage condition.
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
- Controller fault
Operator-safe first checks
- Record whether the message is high or low and any related communication errors.
- Avoid repeated reset attempts if the condition returns.
Trained maintenance / service checks
- The OEM troubleshooting guide directs this condition to Sullair Factory Service.
- Preserve controller configuration and event data before replacement work.
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: 34.