What does TEMP FAULT mean on a Quincy QSI compressor?
Short answer: Temperature probe faulty. If your Quincy QSI series (QSI standard controls) is showing TEMP FAULT, 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 controller detected that the temperature probe is faulty — either an open circuit or shorted — so it cannot trust its temperature reading.
Which machines show this?
Quincy QSI industrial rotary screw compressors with the standard QSI control panel — larger plant-air packages, some fitted with Quincy's integrated refrigerated dryer, whose faults (DRYER CONT., DRYER D.P.) appear on the same display without stopping the compressor. The QSI panel reports faults as short text messages — OVERLOAD, HIGH TEMP, SUMP HAT, TEMP FAULT — rather than numeric codes, so search the exact wording on your display. "Sump" in these messages means the fluid separator vessel, and "fluid" is Quincy's term for the compressor lubricant. Faults clear from the panel after the cause is corrected; the manual keeps the electrical enclosure strictly off-limits to unqualified hands.
What causes it?
- Temperature probe failed open or shorted
- A wiring problem between the probe and the controller
- Occasionally a transient that clears on a power cycle
Can you fix it yourself?
One power cycle is worth trying. Beyond that, no — and do not run the machine on a dead probe, because its high-temperature protection depends entirely on that sensor.
Step by step — what to try, in order:
- Note the exact message and any temperature reading shown
- Power the unit down, wait, restore power, and see if the fault clears
- Do not run the compressor with a known-bad temperature probe — high-temperature protection depends on it
When do you need a technician — and why?
Probe and wiring diagnosis is electrical work at the control cabinet, and until it's done the machine has no working over-temperature protection — the one safeguard standing between it and a cooked airend.
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 TEMP FAULT mean on a Quincy QSI series (QSI standard controls)?
Temperature probe faulty. The controller detected that the temperature probe is faulty — either an open circuit or shorted — so it cannot trust its temperature reading.
Can I fix TEMP FAULT on a Quincy QSI series (QSI standard controls) myself?
One power cycle is worth trying. Beyond that, no — and do not run the machine on a dead probe, because its high-temperature protection depends entirely on that sensor.
When does TEMP FAULT on a Quincy QSI series (QSI standard controls) need a technician?
Probe and wiring diagnosis is electrical work at the control cabinet, and until it's done the machine has no working over-temperature protection — the one safeguard standing between it and a cooked airend. Call a technician right away — diagnosing probe wiring and replacing the sensor is electrical work, and the machine should not run without working temperature protection.
Verified against service documentation: Quincy QSI series (QSI standard controls) documentation for TEMP FAULT (manualslib.com)