Compressor Fault Codes

A fault (or alarm) code is the controller's shorthand for a sensor reading or input that went outside its programmed limits. Codes fall into three groups: warnings, which let the machine keep running; shutdowns, which stop the compressor to protect it; and service reminders, which are timer-based and not faults at all. The code itself never names the broken part — it names the condition the controller measured, so the same code can come from a failed sensor, a wiring fault, or a genuine mechanical problem.

Identify the controller, not just the compressor brand. The controller name is printed on the keypad bezel or the label inside the panel door (for example Elektronikon, Sigma Control, Xe-Series, GD Pilot, Supervisor). Once you know the controller, open its page here and search the code. The same brand often ships three or four different controllers across model years, and their code lists do not match.

Code tables are firmware-specific. Manufacturers renumber alarms between firmware revisions and add codes for optional equipment such as dryers, variable-speed drives, and remote start. Always cross-check the on-screen help text and the OEM manual for your unit's serial number before replacing parts. Treat any published table, including this one, as a starting point.

Only after you know what tripped it. Warnings can often be acknowledged while you investigate, but clearing a shutdown without finding the cause is how a high-temperature trip becomes a seized airend. Resetting also clears the condition data that would have told you what happened. Record the code, the hour meter, and the live sensor readings first.

High discharge temperature, high element/airend outlet temperature, motor overload, emergency stop, low oil pressure, main motor starter fault, high pressure/blowdown failure, and drive (VFD) faults. High temperature leads the list by a wide margin, and its usual causes are a plugged oil cooler, low oil level, a stuck thermostatic valve, a failed cooling fan, or high ambient temperature in the compressor room.

Measure. A temperature-sensor fault that reads an impossible value (far above ambient on a cold machine, or an open/short reading) is almost always the sensor or its wiring. Compare the controller's displayed value against a known-good gauge or infrared thermometer, then check the sensor's resistance against its published curve and the terminal wiring for corrosion and loose screws. Sensor resistance values and terminal assignments are listed on each controller page here.

Usually not for a simple reset, but service menus, timer resets, and setpoint changes are behind a service or factory level. Service-level access is normally granted by the OEM or distributor, and factory levels should be left alone: changing protection setpoints to stop an alarm removes the protection the alarm exists to provide. Where access levels are publicly documented, they are noted on the controller pages.

Start with the brand list on this page and open your controller. Each entry carries its known fault and alarm codes with plain-language meanings and first checks, plus wiring terminals, sensor inputs, known firmware issues, and links to published OEM documentation. Everything works offline in the app, so it is usable in a plant basement with no signal.