Low Sump Pressure — Sensor or Start Fault
The SULLAIR-LOW-SUMP-PRESSURE (Sullair WS Controller) diesel fault code means: Low Sump Pressure — Sensor or Start Fault. This is a moderate severity code.
- DIY difficulty
- moderate
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Common Symptoms
- WS display shows Low Sump Pressure
- Machine may have failed to start or load
Probable Causes (Ranked by Likelihood)
- Bad pressure sensor or connections High
- Machine failed to start / build pressure Moderate
Frequently Asked Questions
What is the low limit?
Per the parameter table the sump pressure (P1) low limit is 5 psig across machine classes — below that the controller flags the condition.
Mechanics Guide Step-by-step diagnosis
Step-by-Step Diagnostic Procedure
The WS Controller is fitted to Sullair STATIONARY electric shop compressors. Portable towable Sullair units (185-class and similar) use different engine-driven controls and a different fault system — this page does not apply to them.
Check the P1 pressure sensor and its connections and wiring.
Confirm the machine actually started and loaded — a failed start reads as low sump pressure.
Factory limits for this condition: P1 low limit 5 psig
Per the factory manual: after resolving a fault condition, press the STOP pad to clear the FAULTED state. If the problem persists after the recommended checks, consult your Sullair distributor or factory service.
Sources 1
This page is built from documented references. Verify against your own service info before repair work.
- Sullair WS Controller User Interface Manual, P/N 02250165-411 (Table 5-1 Troubleshooting Guide)distributor-hosted copy of the official Sullair manualdistributor-hosted copy of an official Sullair factory manual
Commonly Affected Vehicles
- Sullair STATIONARY electric rotary-screw compressors with the WS Controller (including VSD packages)
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