What it means
The controller has detected an abnormal control-electronics supply voltage.
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
- Supply or transformer voltage too high
- Supply or transformer voltage too low
- Excessive load or a short in 24 V control devices
Operator-safe first checks
- Record whether the message says voltage too high or too low.
- Note whether the condition followed a power disturbance or recent electrical work.
- Do not open the electrical enclosure unless trained and authorized.
Trained maintenance / service checks
- Verify supply and transformer connections and adjustments.
- For a low-voltage condition, inspect 24 V control loads, wiring, coils and solenoid circuits for excess load or shorts.
- Confirm measured voltage is within the machine-specific specification.
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: 30.