Why is sump pressure low on my Sullair compressor?
Short answer: Sump pressure below limit. If your Sullair Touch Screen (STS) is showing Low 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 fallen below the set limit. The manual attributes this to a bad pressure sensor or connections, or the machine failing to start properly.
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?
- Bad pressure sensor or its connections
- The machine failing to start and build pressure properly
Can you fix it yourself?
Partly — confirm the machine actually started, restart once after a full blowdown, and sanity-check the displayed pressure against line gauges.
Step by step — what to try, in order:
- Verify the compressor actually started and built pressure
- Restart once after a full stop and blowdown
- Note whether the displayed pressure reading looks plausible compared to line gauges
When do you need a technician — and why?
A repeating fault needs the sensor, wiring, and tubing tested by service — the controller can't run a compressor on a pressure reading it can't trust.
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 Low Sump Pressure mean on a Sullair Touch Screen (STS)?
Sump pressure below limit. Compressor sump pressure has fallen below the set limit. The manual attributes this to a bad pressure sensor or connections, or the machine failing to start properly.
Can I fix Low Sump Pressure on a Sullair Touch Screen (STS) myself?
Partly — confirm the machine actually started, restart once after a full blowdown, and sanity-check the displayed pressure against line gauges.
When does Low Sump Pressure on a Sullair Touch Screen (STS) need a technician?
A repeating fault needs the sensor, wiring, and tubing tested by service — the controller can't run a compressor on a pressure reading it can't trust. Call service to check the pressure sensor, wiring, and tubing if the fault repeats.
Verified against service documentation: Sullair Touch Screen (STS) documentation for Low Sump Pressure (sullair.com)