Why is sump pressure high on my Sullair compressor?
Short answer: Sump (receiver tank) pressure above limit. If your Sullair Touch Screen (STS) is showing High Sump Pressure, the controller has logged a specific, documented condition. This page covers what it means, what causes it, what you can safely fix yourself, and when — and why — it takes a technician.
What exactly is the machine telling you?
Compressor sump pressure has risen above the set limit, typically because an unloading component (poppet, Sullicon control, spiral valve, blowdown or pneumatic valve) or a control solenoid has failed.
Which machines show this?
current-generation Sullair stationary rotary screw compressors — the LS-series and related packages built from the late 2010s onward — fitted with the 10-inch Sullair Touch Screen (STS) controller. The STS spells out problems as plain-English named faults and warnings ('High Temperature 1', 'Failed to Unload', 'Replace I/O Battery') rather than bare code numbers, and pairs them with live readings and a Recommended Service screen that tracks filter and separator hours. Warnings keep the machine running; faults shut it down until reset. Practical tip: before clearing anything, photograph the fault screen and the Recommended Service page — the service-hour counters usually point straight at the consumable that caused the trip.
What causes it?
- A failed unloading component — poppet, Sullicon control, spiral valve, blowdown or pneumatic valve
- A control solenoid not shifting
- The unit simply not unloading when demand stops
Can you fix it yourself?
No — beyond a full stop, blowdown, one restart, and recording the trip pressure, this is not in-house work.
Step by step — what to try, in order:
- Press Stop, let the machine blow down fully, and attempt one restart
- Listen/observe whether the unit actually unloads when demand stops
- Record the sump pressure reading shown at the time of the trip for the technician
When do you need a technician — and why?
Diagnosing control valves, solenoids, and the regulator happens on a pressurized system; never loosen fittings while the sump holds pressure.
If it does come to a service call and you're in Nashville, TN or Birmingham, AL, we maintain independently compiled lists of local companies that service industrial air compressors — real businesses with verified contact information, none of whom paid to be listed.
Related questions
What does High Sump Pressure mean on a Sullair Touch Screen (STS)?
Sump (receiver tank) pressure above limit. Compressor sump pressure has risen above the set limit, typically because an unloading component (poppet, Sullicon control, spiral valve, blowdown or pneumatic valve) or a control solenoid has failed.
Can I fix High Sump Pressure on a Sullair Touch Screen (STS) myself?
No — beyond a full stop, blowdown, one restart, and recording the trip pressure, this is not in-house work.
When does High Sump Pressure on a Sullair Touch Screen (STS) need a technician?
Diagnosing control valves, solenoids, and the regulator happens on a pressurized system; never loosen fittings while the sump holds pressure. Call a service technician — diagnosing control valves, solenoids, and the pressure regulator on a pressurized system is not a DIY job.
Verified against service documentation: Sullair Touch Screen (STS) documentation for High Sump Pressure (sullair.com)