Air Compressor Fault Codes Explained

Compressor controller displays equipment operating abnormalities through fault codes. Maintenance personnel can quickly locate problems based on codes.

E001 Discharge Temperature Too High

Six or seven out of ten service calls are this fault.

Temperature alarm threshold varies by brand. Atlas Copco GA series defaults to 221°F. Fusheng SA series 212°F. Ingersoll Rand most models set at 230°F. Exceeds this value, controller shuts down for protection.

Maintenance

Oil Cooler Inspection & Cleaning

Vast majority of cases, problem is in oil cooler. Fins caked with dust causes heat exchange efficiency to drop. Textile mills, cement plants, flour mills, these heavy dust environments especially bad. Some plants go two months without cleaning fins and report high temperature. Fix is simple. Remove cooler housing, use compressed air to blow in reverse direction. Ingersoll Rand fins have small spacing, keep air pressure below 45 psi. Too high pressure bends the fins, makes it worse. Internal oil passages with scale need to be removed and soaked with circulating cleaner.

Oil level insufficient ranks second. Many times not a leak, but return oil line blocked. Oil accumulates in separator tank, oil level on airend side slowly drops. So when you see low oil level, don't rush to add oil. Check return oil line first.

Sensor failure probability actually not high, but have encountered it. Test method is use infrared thermometer gun on discharge pipe surface, compare with controller display value. Deviation exceeds 15°F, basically can confirm sensor drift. PT100 type sensor can be removed and resistance measured. 212°F corresponds to about 138.5Ω.

Southern summer machine room temperature itself is high. Ventilation also bad. Just cleaning cooler might not work. Need to install axial fan at exhaust opening to pull hot air out.

E002 Discharge Pressure Too High

This fault most of the time is not compressor's problem.

Downstream air-using equipment suddenly stopped. Air in pipe network has nowhere to go. Pressure spikes instantly and triggers alarm. VFD machine responds fast but still takes a few seconds. By then pressure spike already passed. Reset and continue running, no need to repair.

Pressure sensor failure probability very low. Temporarily connect a pressure gauge on discharge line to compare and you'll know.

When troubleshooting E004 motor overload, first check if there's E002 record. Discharge pressure running high directly increases compression power. Current goes up with it. Solve pressure problem and overload might be gone.

E003 Discharge Pressure Too Low

This fault needs to be judged together with load indicator light.

Load light on but pressure won't come up, problem is at inlet side. Most common is inlet valve not fully open. Fusheng butterfly-type inlet valve uses servo cylinder to push. Seal ring aged and leaks, then valve plate can't reach position. Atlas Copco uses solenoid valve to control inlet valve. Solenoid coil burned or control wire broken, valve doesn't actuate. Also air filter blocked. Textile mill air filters need changing every two or three months. Remove filter element and run unloaded to test. If pressure returns to normal, it's the air filter.

Load light on, pressure also has some, just can't reach setpoint. Mostly internal leakage. Separator tank gasket aged, check valve not sealing, safety valve lift pressure dropped. Check these locations one by one. Sullair separator tank flange face is large. Gasket having problems is relatively higher probability.

E004 Motor Overload

First measure voltage.

Three-phase voltage should be within ±5% of rated value. Many industrial parks during daytime peak usage, voltage drops below 360V. Motor to maintain power output, current has to rise. Recommend installing voltmeter in control cabinet so you can see anytime. Voltage chronically low, install voltage stabilizer.

Voltage no problem, then look at pressure setting. Discharge pressure adjusted from 115 psi to 145 psi, 30 hp model current increases about 15%. Some users think higher pressure is good, store more air. Actually damages motor badly. Pressure setting don't exceed nameplate rated discharge pressure.

Mentioned earlier in E002, discharge pressure running high also causes overload. Rule out pressure problem first.

Diagnostics

Motor Control Systems

Components

Drive Motor Assembly

Mechanical causes include airend bearing wear, rotor clearance enlarged, insufficient lube oil causing increased friction. Before barring to check if it turns smoothly, first confirm separator tank is depressurized. Barring under pressure has caused accidents.

Carrier screw machines have one easy pitfall. Y-delta switching timer setting wrong. Switching moment current impact triggers protection. Generally set to switch 8 to 12 seconds after startup is appropriate.

E005 Motor Overheating

Related to E004. Motor running at overload edge long-term, temperature rise definitely high. Before handling E005, first flip through recent records for E004 alarms.

Ambient temperature exceeds 104°F, motor cooling capacity noticeably drops. Northern summer midday, machine room temperature often 113°F and up. Motor housing dust accumulation affects heat dissipation. Blow it clean, can drop 10-15°F.

Bearing temperature can be measured with infrared thermometer gun through end cover vent holes. Normal doesn't exceed 160°F. Noticeably hot, time to change bearings. When changing bearings, grease amount should be appropriate. Too much heats up, too little wears.

E006 Oil Separator Differential High

Differential setpoint usually 12-15 psi. Exceeds this means separator element needs changing.

Separator element normal life 3,000 to 4,000 hours. Humid environments or poor oil quality shortens to 2,000 hours. After differential alarm, continuing to run sick isn't worth it. Every 1.5 psi increase in differential uses about 1% more electricity.

Buying separator element pay attention to model. Sullair and Atlas Copco specs aren't interchangeable. Domestic substitute elements much cheaper. Quality varies widely. Choose products from decent size filter manufacturers. No-name elements blocking after two months, seen plenty.

Return oil line blockage also causes high differential. This line has only 1/8 inch ID. Inside also has orifice. Oil sludge easily blocks it. Remove and poke through with thin wire. Check return oil check valve at same time.

Lubricating oil turned black or showing emulsification, change whole machine's oil. Synthetic oil has good oxidation resistance, can last 8,000 hours. Mineral oil tops out at 4,000 hours.

Mentioned earlier in E001, high temperature and high differential appearing together, first consider oil problem.

E007 Startup Failure

Start with simple stuff.

Power phase loss, use multimeter to measure three-phase voltage. One phase noticeably low or zero, that's phase loss. Break point might be at circuit breaker, fuse, contactor contacts. Check one by one.

Separator tank residual pressure too high, startup load heavy, star-delta switching current impact triggers protection. Normal shutdown, inlet valve closes, internal pressure bleeds slowly through blowoff valve. Few minutes later drops to below 30 psi. Blowoff valve solenoid stuck or bleed hole blocked, residual pressure can't bleed. Manually press blowoff valve to release pressure, then start.

Main contactor failure shows as not engaging after pressing start, or engages then immediately trips. Coil burned, measure resistance and you'll know. Contacts badly pitted, visible to naked eye. Siemens, Schneider contactors are stable. Domestic ones cheap but shorter life. Depends how plant chooses.

E008 Sensor Failure

Controller will display which specific sensor has problem.

Temperature sensor and pressure sensor fail most easily. But before replacing sensor, first tighten all wire terminals. Compressor vibration is heavy. Loose wiring causing unstable signal is quite common. Tightened and fault disappears, also common.

Pressure sensor diaphragm damaged causes signal drift. Connect a standard pressure gauge to compare. PT100 temperature sensor measure resistance. 4-20mA output type measure current signal. Controller parameters can show sensor real-time signal value. Doesn't match actual condition, then sensor itself has problem.

Control board failure probability low. Only consider after sensors and wiring both ruled out. Can try connecting sensor to spare channel. Spare channel also abnormal, then it's control board issue.

E009 Fan Failure

Cooling

Fan Motor Assembly

Service

Winding Inspection

Repair

Bearing Replacement

Fan motor burned, most direct sign is doesn't turn when powered. Measure winding resistance, three phases should be basically equal. One phase noticeably high or infinite, that's winding open circuit. Fan motors are low power. Replacing one isn't expensive.

Thermal overload keeps tripping means motor current running high. Might be bearing seized or impeller rubbing housing. After reset, turn impeller by hand. Hard to turn needs repair.

Before checking motor, first check if wires are broken. Both in terminal box and in control cabinet. Some models, fan powered separately by VFD. VFD fault, fan also doesn't turn.

Northern winter below freezing, fan motor oil seal might freeze stiff. Cold start moment current high triggers protection. Before starting, use heat gun to warm it up a few minutes.

E010 VFD Fault

Overcurrent, check motor insulation, check if output cable is shorted, check if motor parameters set correctly. Overvoltage or undervoltage is input power issue. Overheating, check if VFD cooling fan is turning, is filter screen blocked, is installation location ventilation good.

Communication interrupt means controller can't read VFD status. Check communication wire and terminals for oxidation. RS485 communication wiring has polarity requirement. A to A, B to B. Connected backwards, won't communicate. Baud rate and station address parameters also need to be verified.