What it means
A configured analog input is reading abnormally low in a way that indicates a sensor or wiring problem.
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
- Pressure transducer, temperature probe or other analog sensor failure
- Wiring or connection fault
Operator-safe first checks
- Record the full channel name/number shown after AN_.
- Compare the suspect reading with other safe-to-view process indications.
Trained maintenance / service checks
- Inspect the sensor circuit and wiring.
- Test the sensor using the machine-specific diagnostic values before replacement.
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: 32.