What does a Sensor Fail message mean on a Sullair Supervisor?
Short answer: Pressure or temperature sensor failure. If your Sullair Supervisor Controller is showing P1-P4 / T1-T5 Sensor Fail, 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?
The named pressure transducer or temperature probe, or its wiring, has failed — the controller reads an impossible value (e.g., over 500 psi/°F or below -40) and flags the sensor circuit.
Which machines show this?
older large-frame Sullair rotary screw compressors — flooded-screw and two-stage industrial packages from the Supervisor era, many still running in plants today. The Supervisor reports by channel: temperatures are T1 through T5, pressures P1 through P4, and differential pressure dP1, so a fault reads like 'T2 Discharge High' or 'P1 Sump Pressure High' rather than a code number. Flooded screws warn at 225 °F on T1 and fault at 235 °F delayed or 255 °F immediate; sensor failures are flagged when a channel reads an impossible value. Practical tip: always record which channel number tripped — T-numbers and P-numbers map to specific probes on the machine, and that number is the first thing a Sullair technician will ask for.
What causes it?
- The named transducer or probe reading an impossible value (over 500 or below -40)
- Failed sensor wiring or a loose connection
Can you fix it yourself?
Sometimes — a locked-out connector and wiring check, one reset, and a note of which sensor number failed.
Step by step — what to try, in order:
- With power locked out, check that the sensor connector is seated and wiring is undamaged
- Reset and restart once to rule out a loose connection
- Note which sensor number failed for the service call
When do you need a technician — and why?
A returning failure means the sensor needs testing and replacement — the controller cannot protect the machine on a reading it knows is impossible.
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 P1-P4 / T1-T5 Sensor Fail mean on a Sullair Supervisor Controller?
Pressure or temperature sensor failure. The named pressure transducer or temperature probe, or its wiring, has failed — the controller reads an impossible value (e.g., over 500 psi/°F or below -40) and flags the sensor circuit.
Can I fix P1-P4 / T1-T5 Sensor Fail on a Sullair Supervisor Controller myself?
Sometimes — a locked-out connector and wiring check, one reset, and a note of which sensor number failed.
When does P1-P4 / T1-T5 Sensor Fail on a Sullair Supervisor Controller need a technician?
A returning failure means the sensor needs testing and replacement — the controller cannot protect the machine on a reading it knows is impossible. Call a technician to test and replace the sensor if the failure message returns.
Verified against service documentation: Sullair Supervisor Controller documentation for P1-P4 / T1-T5 Sensor Fail (best-aire.com)