ELGi Compressor Fault Codes: Full Diagnostic Guide

ELGi Compressor Fault Codes - Quick Reference

ELGi compressors (EG, EN, AB series) use an electronic controller that monitors temperature, pressure, motor current, and maintenance intervals. Alarm messages appear on the display with a fault description and recommended action.

Safety Before You Start

Rotary screw compressors store both electrical and mechanical energy that can injure you during troubleshooting.

• Lock out and tag out the main disconnect before opening any electrical panel or removing guards. Follow your site’s LOTO procedure and OSHA 29 CFR 1910.147.
• Fully vent the receiver tank and air lines before opening any pressurized fitting, separator vessel, or filter housing. ELGi units hold pressure in the separator tank even after the compressor stops; check the gauge reads zero before loosening anything.
• Let the compressor cool before working near the airend, oil cooler, or discharge piping. Discharge temperatures during normal operation commonly exceed 180°F and can cause serious burns.
• Never open the oil fill port or separator tank while the unit is pressurized or running. Oil under pressure can spray and cause chemical burns or eye injury.
• Keep hands and tools clear of the drive belt or coupling and fan blades whenever the unit could start, including during auto-restart cycles on units with unattended operation enabled.
• If you are not trained on compressed-air systems or unsure about isolating stored pressure on this specific model, stop and call a qualified technician.

Tools You Will Need

• Digital multimeter for voltage and continuity checks
• Pressure gauge or manifold set to verify differential pressure readings independent of the controller display
• Compressed air source and blow gun for cleaning cooler fins (use eye protection)
• Oil analysis kit or dipstick/sight glass reference for oil level and condition
• ELGi controller manual or fault code reference for your specific model (EG, EN, or AB series controllers differ)
• Infrared thermometer for cooler and airend surface temperature checks

Most Common Faults

High Discharge Temperature

ELGi compressors are known for robust cooling systems but they still trip on high discharge temp when oil is low, coolers are dirty, or ambient temperature is excessive. Follow this sequence rather than jumping straight to parts replacement:

1. Confirm the alarm and note whether it appeared at startup, under steady load, or after running for an extended period. Timing narrows the cause.
2. With the machine stopped and cooled, check the oil sight glass. Oil should be at the correct level marked on the glass; low oil reduces cooling capacity and lubrication together.
3. Inspect the oil cooler and after-cooler fins for dust, oil film, or debris buildup. Clean with compressed air directed from the clean side toward the dirty side, following the direction that pushes debris out rather than deeper into the fins.
4. Confirm the cooling fan spins freely and reaches full speed. A fan running slow from a failing motor or worn bearing reduces airflow without stopping entirely, which can be easy to miss on a quick visual check.
5. Check ambient temperature in the compressor room. ELGi ratings assume a maximum ambient, typically in the 104 to 115°F range depending on model; a poorly ventilated compressor room in summer can push discharge temperature past the trip point even with clean equipment.
6. Measure discharge temperature with an infrared thermometer at the airend outlet piping and compare to the controller’s displayed reading. A large mismatch points to a failed or drifting temperature sensor rather than an actual overheat condition.
7. If oil, cooler, fan, and ambient conditions all check out and the sensor reading matches an independent measurement, the airend itself may be developing internal wear or a coupling alignment issue generating extra heat. This calls for a qualified technician.

Air/Oil Separator Choked

The separator element removes oil droplets from compressed air. As it loads up with oil and debris, the differential pressure across it rises. When the DP exceeds the setpoint (usually around 10 psi on most ELGi models, though this varies by controller configuration), the controller alarms.

1. Fully depressurize the separator tank and confirm zero pressure on the gauge before opening any fitting.
2. If the controller displays a live differential pressure reading, record it before shutting down. If not, connect a manifold gauge across the separator inlet and outlet ports per the service manual.
3. Replace the separator element rather than simply resetting the alarm and continuing to run. A choked separator that keeps running pushes oil carryover downstream into the air system, which can contaminate tools, actuators, or process equipment.
4. While the separator tank is open, inspect the scavenge line (the small tube that returns separated oil to the airend) for kinks, clogs, or disconnection. A blocked scavenge line will choke a brand-new separator element quickly.
5. After replacing the element, run the compressor and verify the differential pressure reading drops to a normal baseline within the first few minutes of operation.

Low Oil Pressure

1. Check oil level first with the machine stopped, using the sight glass or dipstick per the model’s service points.
2. Inspect the oil filter. A clogged filter on initial cold startup can drop pressure before oil flow is established, especially in cold ambient conditions where oil viscosity is higher.
3. If oil level and filter are fine, inspect the oil pressure sensor and its wiring harness for corrosion, loose pins, or chafed insulation.
4. Verify the oil pump (on models with a dedicated oil pump rather than airend-pressure-driven lubrication) is turning and not seized.
5. If pressure reads low on an independent gauge as well as the controller, and oil, filter, and sensor all check out, the oil pump or internal lubrication passages may need professional inspection.

Motor Overload

A motor overload alarm means the motor drew more current than the overload relay or controller setpoint allows.

1. Verify supply voltage at the compressor’s input terminals with the machine under load. Voltage more than about 10 percent below nameplate rating causes the motor to draw excess current to deliver the same power.
2. Check for a phase imbalance on three-phase units. Measure voltage between each pair of phases and compare; imbalance above roughly 2 percent stresses the motor and can trigger nuisance trips.
3. Confirm the compressor is not being asked to deliver above its rated output, for example from a downstream leak or an added piece of equipment that increased demand beyond the compressor’s capacity.
4. Inspect the motor and coupling for binding, contamination, or bearing wear that would increase mechanical load on the motor.
5. If voltage, phasing, and demand all check out, have a qualified electrician verify the overload relay setpoint matches the motor nameplate current and test the motor’s running current directly with a clamp meter.

Sensor Failure

1. Identify which sensor triggered the fault from the controller display: discharge temperature, oil temperature, or pressure transducer readings are the most common.
2. Visually inspect the sensor’s wiring harness for corrosion, chafing, or a loose connector, especially near hinge points or areas exposed to vibration.
3. Where practical, compare the sensor’s reading to an independent measurement, such as an infrared thermometer for a temperature sensor or a calibrated gauge for a pressure transducer.
4. If the sensor reads open or shorted on a multimeter continuity check with the harness disconnected, replace the sensor rather than continuing to reset the fault.

Service Required

This is not a mechanical fault. It means the controller’s maintenance counter has reached a scheduled interval for oil, filter, or separator service. Perform the PM tasks listed in the ELGi service manual for that interval, then reset the counter through the controller menu. Skipping the reset will cause the alarm to reappear even after service is done.

When Resetting the Alarm Is Not Enough

ELGi controllers allow most alarms to be cleared with a reset button once the display no longer shows an active fault condition. Resetting without addressing the underlying cause is the most common mistake technicians make on these units. A separator choked alarm that gets reset repeatedly without element replacement will eventually let oil carry over into the air system. A high discharge temperature alarm reset without cleaning the cooler will trip again within minutes of restart, often sooner each time as heat accumulates. Treat every reset as temporary until you have completed the diagnostic steps for that specific fault.

Parts Often Needed

Need Replacement Parts?

Before ordering, match the compressor part to the model number, electrical rating, and failure symptom. Check current prices on Amazon - prices and availability change frequently.

Jump to Fix

• High discharge temp → Verify oil level → Clean cooler → Check fan
• Separator choked → Replace element → Reset alarm
• Low oil pressure → Check oil level → Replace filter → Inspect sensor

When to Call a Pro

ELGi has a global dealer network. Call an ELGi authorized service center when:

• A fault persists after you have completed the full diagnostic sequence for that alarm and replaced the parts it points to.
• You find evidence of internal airend wear, unusual noise, or vibration that suggests a mechanical problem beyond the cooling and lubrication system.
• The compressor is under warranty; unauthorized parts or service can void coverage.
• You do not have the tools or training to safely depressurize the separator tank or isolate electrical power before working on the unit.
• Motor overload trips continue after voltage, phasing, and demand are confirmed normal, which points to a motor or overload relay issue that needs professional testing.

An ELGi dealer can also run airend diagnostics and verify controller configuration settings that are not accessible through routine troubleshooting.

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