What it means
The variable-frequency drive is reporting that its temperature is too high.
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
- Insufficient VFD ventilation
- Cooling path contamination or restriction
- High ambient temperature
Operator-safe first checks
- Confirm the VFD cooling-air path is not externally obstructed.
- Record ambient temperature and whether the warning occurs under heavy load.
Trained maintenance / service checks
- Ensure adequate ventilation around the VFD.
- Schedule cleaning/maintenance of the drive cooling system before a high-temperature trip develops.
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: 35.