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Atlas Copco Compressor Fault Codes — Quick Reference
Atlas Copco rotary screw compressors with Elektronikon controllers display warnings, service reminders, and shutdown alarms tied to temperature, pressure, motor overload, and sensor faults. The exact code list varies by generation (Elektronikon MkIV, MkV, Graphic, and the newer Elektronikon Touch), so the text on your display may read slightly differently than the entries below. These are the alarm families technicians see most often across generations.
If your controller shows a numeric or alphanumeric code that is not listed here, do not guess at its meaning. Open the Elektronikon manual for your compressor’s exact controller generation and serial range, or call Atlas Copco service. Guessing at fault meanings on a compressor with stored air pressure and rotating equipment is how people get hurt.
| Alarm | Meaning | Quick Fix |
|---|---|---|
| High Element Outlet Temp | Compressor running too hot | Check coolers and oil level |
| High Dew Point | Dryer not performing | Check refrigerant dryer and condensers |
| Main Motor Overload | Motor current too high | Check load and motor amps |
| Sensor Fault | Temp or pressure sensor signal bad | Check sensor wiring |
| Emergency Stop | E-stop circuit open | Reset E-stop and inspect circuit |
| Service Due | Preventive maintenance interval reached | Perform service and reset counter |
| Separator Differential High | Oil separator restricted | Replace separator |
| Low Oil Pressure | Lubrication fault | Check oil level and filter |
Most Common Faults
High Element Outlet Temperature
This is one of the most common shutdown causes on rotary screw compressors. Dirty coolers, low oil level, a failed cooling fan, a stuck thermostatic valve, or high ambient temperature all drive discharge temperature up. The Elektronikon typically warns before it trips, so you often get advance notice on the display before a full shutdown.
Start by blowing out the oil cooler and aftercooler with dry compressed air in the opposite direction of normal airflow. Fins packed with dust act like insulation and choke off heat rejection. Confirm the cooling fan actually spins at full speed and the fan belt (on belt-driven units) is not slipping. Check the oil level against the sight glass while the machine is stopped, since low oil starves the airend of the film it needs for both lubrication and cooling. If the room the compressor sits in has poor ventilation or is sharing intake air with other heat sources, ambient temperature alone can push the element outlet temperature past the alarm threshold even with a clean machine.
Separator Differential High
A restricted oil separator creates excessive pressure drop and poor oil carryover control. The Elektronikon monitors the pressure differential across the separator element and alarms when it climbs past the safe range, which usually points to varnish and sludge buildup inside the element media. Replace the separator element if the differential stays high after service; there is no cleaning procedure that restores a plugged separator to spec. Running too long with a plugged separator increases energy use, drives oil carryover into the downstream air system, and can eventually starve the compressor of oil pressure entirely.
Motor Overload
Check line voltage, current balance across all three phases, and actual compressed air demand against the compressor’s rated capacity. A compressor cycling between loaded and unloaded modes too aggressively may need control tuning or a storage tank review, not just a motor reset. Also check the drive coupling or belt tension on units that are not direct-drive, since a misaligned coupling or slipping belt increases the load the motor has to fight to maintain speed.
High Dew Point
This alarm means the integrated or standalone refrigerant dryer is not pulling enough moisture out of the compressed air stream, which risks water carryover into the plant’s air system. Check that the dryer’s condenser coils are clean, the refrigerant charge has not leaked down, and the condensate drain is actually cycling and not stuck open or closed. A drain stuck open bleeds off system pressure continuously; one stuck closed lets condensate pool inside the dryer and defeats the whole purpose of having it.
Low Oil Pressure
Low oil pressure alarms point to a lubrication problem that, if ignored, leads to airend bearing and rotor damage. Confirm the oil level first, then check the oil filter for a high differential that suggests it is loading up with debris. On oil-injected screw compressors, the system pressure itself typically drives oil circulation, so a low discharge pressure setpoint or a failing minimum pressure valve can starve the airend of oil flow even when the oil pump and filter are fine.
Diagnostic Sequence
Work through these steps in order. Do not skip ahead to parts replacement before confirming the simpler causes first, since most Elektronikon alarms trace back to airflow restriction, oil condition, or a sensor issue rather than a failed major component.
- Read the alarm history on the Elektronikon display. Most controllers log the last several alarms with a timestamp and running hours. A single isolated alarm is often incidental (a momentary voltage sag, for example); a recurring alarm on the same code is the one that needs root-cause work.
- Record the actual sensor readings, not just the alarm. Pull up the live values for element outlet temperature, separator differential, oil pressure, and dew point on the display before you touch anything. Compare these against the nameplate and manual specs for your model.
- Isolate power and lock out before opening any panel. See Safety below. Do not open the enclosure or touch cooling fins, belts, or couplings while the unit is running or before it has fully bled down.
- Inspect and clean the cooling package. Remove dust and debris from the oil cooler and aftercooler fins. Confirm the cooling fan spins freely, at full speed, and in the correct direction.
- Check oil level, oil condition, and oil filter condition. Dark, gritty, or foamy oil signals a problem beyond routine wear. Replace oil and filter per the service interval if either looks questionable, not just when the counter says so.
- Check the separator differential reading against spec. If it is elevated and cleaning the cooling package did not bring it down, plan on separator replacement.
- Verify electrical supply. Check line voltage on all three phases and confirm current draw is balanced. An imbalanced or low-voltage supply causes nuisance overload trips that look like a compressor problem but are actually an upstream electrical issue.
- Check sensor wiring and connectors for damage or corrosion if the display shows a sensor fault rather than an out-of-range reading. A loose connector or chafed wire can mimic a real process fault.
- Clear the alarm and run a monitored test cycle. After addressing the suspected cause, reset the alarm per the Elektronikon menu and watch the readings through a full load/unload cycle before returning the compressor to unattended service.
- Escalate to a qualified technician if the alarm recurs after these steps, or if it involves the main motor, airend, or any high-pressure component you are not equipped to service.
Tools You’ll Need
- Elektronikon controller manual or menu access for your specific generation (MkIV, MkV, Graphic, Touch)
- Digital multimeter for voltage and current checks
- Clamp meter for three-phase current balance
- Dry compressed air source (or shop vacuum) for cleaning cooler fins
- Replacement oil filter and correct-spec compressor oil on hand before starting service
- Lockout/tagout kit rated for the compressor’s disconnect
- Manufacturer-specified oil/air separator element if differential is out of spec
Safety: Lockout/Tagout and Stored Energy
Rotary screw compressors combine three hazards that make shortcuts dangerous: electrical power to the main motor, stored compressed air pressure in the receiver tank and piping, and hot surfaces on the airend, coolers, and discharge piping.
Before opening any panel or performing any service:
- De-energize the compressor at the disconnect switch and apply your own lock and tag. Do not rely on the Elektronikon’s stop button alone; it stops the control logic, not the incoming power.
- Bleed the receiver tank and downstream piping down to zero pressure using the manual drain or bleed valve, and confirm zero on a gauge before opening any fitting.
- Allow the airend, oil cooler, and discharge piping to cool before handling. These surfaces run well above ambient temperature during normal operation and can cause burns for some time after shutdown.
- Verify zero energy state before beginning work, not just before you personally feel ready. A second technician assuming the machine is off because a coworker said so is a common cause of compressor incidents.
Parts Often Needed
| Part | Notes |
|---|---|
| Air/oil separator | Major service item |
| Oil filter | Replace with separator service |
| Temperature sensor | Common after vibration and heat cycling |
| Cooling fan / contactor | Common on overheats |
Need Replacement Parts?
Before ordering, match the commercial equipment part to the model number, electrical rating, and failure symptom. Check current prices on Amazon - prices and availability change frequently.
When to Call a Pro
If the compressor repeatedly trips on temperature or motor overload after routine service, involve an Atlas Copco technician. Screw compressor control problems and internal airend wear are not guess-and-check repairs.
Call a qualified technician immediately if you see any of the following, rather than continuing to reset and restart the unit:
- The alarm recurs within one or two load cycles after a reset, which suggests the underlying cause was not actually corrected.
- Oil pressure or oil level alarms combined with unusual noise from the airend, since this can indicate bearing or rotor damage already in progress.
- Any sign of oil or air leaking from the airend housing, shaft seal, or discharge piping under pressure.
- Electrical faults that trip upstream breakers or show burn marks, discoloration, or a burning smell near the motor starter or control panel.
- Any fault code on the display that is not documented in your compressor’s manual for its specific controller generation and serial range. Do not extrapolate a meaning from a similar-looking code on a different model.
A compressor technician with access to Atlas Copco’s diagnostic software and current parts catalog can confirm sensor calibration, pull historical trend data the Elektronikon stores internally, and verify whether a component needs replacement versus adjustment. For a machine under warranty, unauthorized internal service can also void coverage, so check the warranty terms before opening the airend housing yourself.
Preventive Maintenance to Reduce Fault Frequency
Many of the alarms above become far less frequent with a maintenance schedule that keeps ahead of the wear curve instead of reacting to it:
- Clean cooler fins on a fixed interval tied to your facility’s dust and airborne debris level, not just when the temperature alarm fires.
- Change oil and the oil filter at the manufacturer’s stated hours or calendar interval, whichever comes first, since oil breaks down chemically even under light duty.
- Track separator differential trend over time rather than waiting for the alarm threshold. A slowly climbing differential over several months tells you a replacement is coming before it becomes an emergency shutdown.
- Keep a log of every alarm, its running-hours timestamp, and the corrective action taken. This log is the single most useful diagnostic tool you can hand to a technician when a fault becomes chronic.