What does a T1 or T2 High fault mean on a Sullair Supervisor?
Short answer: High temperature fault at a monitored probe. If your Sullair Supervisor Controller is showing T1-T5 High (e.g. T2 Discharge High), 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?
A monitored temperature (interstage, discharge, or oil) exceeded its limit — on flooded screws T1 warns at 225°F and faults at 235°F delayed / 255°F immediate. Causes include ambient above 105°F, low fluid, thermal valve issues, dirty or plugged coolers, low water flow, or sensor failure.
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?
- Ambient above 105°F, low fluid, or a thermal valve issue
- Dirty or plugged coolers, or low water flow on water-cooled units
- Sensor failure at the flagged probe
- On flooded screws, T1 warns at 225°F and faults at 235°F delayed / 255°F immediate
Can you fix it yourself?
Often, yes — ventilation, fluid level, cooler cleaning, and water-flow checks cover the documented causes an operator can reach.
Step by step — what to try, in order:
- Improve ventilation if ambient exceeds 105°F (41°C)
- Check and replenish fluid level once the unit is stopped and cool
- Clean cooler fins and fan
- On water-cooled units, verify valves are open and water flow is adequate
When do you need a technician — and why?
A repeating fault after those checks means thermal valve, plugged cooler cores, or a failing probe — technician diagnosis with proper instruments.
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 T1-T5 High (e.g. T2 Discharge High) mean on a Sullair Supervisor Controller?
High temperature fault at a monitored probe. A monitored temperature (interstage, discharge, or oil) exceeded its limit — on flooded screws T1 warns at 225°F and faults at 235°F delayed / 255°F immediate. Causes include ambient above 105°F, low fluid, thermal valve issues, dirty or plugged coolers, low water flow, or sensor failure.
Can I fix T1-T5 High (e.g. T2 Discharge High) on a Sullair Supervisor Controller myself?
Often, yes — ventilation, fluid level, cooler cleaning, and water-flow checks cover the documented causes an operator can reach.
When does T1-T5 High (e.g. T2 Discharge High) on a Sullair Supervisor Controller need a technician?
A repeating fault after those checks means thermal valve, plugged cooler cores, or a failing probe — technician diagnosis with proper instruments. Call service if the high-temperature fault repeats after these checks — thermal valve, plugged cooler cores, or a failing probe require a technician.
Verified against service documentation: Sullair Supervisor Controller documentation for T1-T5 High (e.g. T2 Discharge High) (best-aire.com)