What it means
Communication has been lost between the STS controller and the spiral-valve motor-driver module.
Electronic spiral-valve operation is blocked until the communication problem is corrected.
Likely causes
- Loss of communication between STS I/O/controller and spiral motor driver
- Power-cable connection problem at the driver module
- Communication-cable problem
- Incorrect driver-switch settings after replacement
Operator-safe first checks
- Record whether the fault appeared after controller/driver service or replacement.
- Do not reach into the machine or reseat internal electrical connections while energized.
Trained maintenance / service checks
- With electrical isolation and lockout in place, inspect the driver power connection.
- Check the communication cable between the STS I/O module and spiral motor driver.
- If the driver was replaced, verify its switch settings against the service procedure.
Can the compressor keep running?
Do not bypass the fault. The affected capacity-control mechanism is unavailable until communication is restored.
Source confidence
OEM VERIFIED
Sullair points to driver power/communication cabling and driver settings after replacement.
Source: Sullair STS Controller User Manual, part 02250241-178 R01. Referenced manual page(s): 20, 34.