Ingersoll Rand is one of the most trusted names in compressed air. A well-maintained Ingersoll Rand oil-injected (oil-flooded) rotary screw air compressor will normally work for tens of thousands of hours with relatively few difficulties. But no compressor is safe from neglect. Eventually the skipped oil changes, plugged coolers and used up consumables will show up as high temps, oil in the air line, pressure difficulties or nuisance excursions.
This tutorial covers the 10 most common issues we find on Ingersoll Rand rotary screw compressors - including SSR, UP-series, R-series and related machines operated by either theIntellisys microprocessor controlleror olderrelay-based control panels. Each fault will show the possible reasons, how to test them and what to do.
Safety First:Stop the unit, isolate and lock out the electrical supply, vent system pressure completely before opening any panel or component. Hot oil and compressed air can cause severe harm. Electrical checks must be carried out by qualified people only.
Quick Reference: Fault Symptoms at a Glance
| # |
Symptom |
Most Likely Causes |
| 1 |
High discharge temperature (above 100 °C / 212 °F) |
Low coolant, dirty oil cooler, clogged oil filter, thermostatic valve, fan/airflow, ambient temperature |
| 2 |
High oil consumption / oil in compressed air |
Overfilled coolant, blocked scavenge line, damaged separator element, low discharge pressure |
| 3 |
Low system pressure |
Air demand exceeds output, blowdown valve leaking, inlet valve or loading cylinder fault, pressure setting |
| 4 |
Discharge pressure too high |
Inlet valve not closing, load solenoid (1SV), pressure sensor/switch, setting too high |
| 5 |
High running current or trip during operation |
Low voltage, over-pressure, blocked separator element, airend or motor fault |
| 6 |
Unit will not start |
Blown fuse, temperature switch, thermal overload, transformer, controller power, unreset fault |
| 7 |
High starting current or trip on start-up |
Low voltage, star-delta timing, loading cylinder not reset, inlet valve stuck open |
| 8 |
Fan motor overload |
Fan damage, motor fault, clogged cooler, high discharge duct back-pressure |
| 9 |
Frequent loading/unloading or won't unload |
Leaks, undersized receiver, pressure band too narrow, 1SV / inlet valve fault |
| 10 |
Water or emulsified oil in the coolant |
Low operating temperature, short-cycling, condensate not draining |
Fault 1: High Discharge Temperature Over100°C/212°F
Normal airend discharge temperature on an Ingersoll Rand screw compressor is usually 80–95 °C (176–203 °F) depending on ambient circumstances. Intellisys will send you an alert and shut the machine down at around 109 °C (228 °F), as the temperature rises. Persistent readings above 100 °C indicate something is amiss and should be checked before a trip happens.
| Possible Cause |
How to Check |
Fix |
| Coolant level too low |
With the unit running loaded, oil should be visible at roughly the midpoint of the sight glass. |
Top up with the correct Ingersoll Rand coolant (e.g. Ultra Coolant / SSR Ultra Plus). Investigate the cause of loss. |
| Oil cooler fins dirty or blocked |
Visual inspection; large temperature difference between cooler inlet and outlet air. |
Blow out cooler with low-pressure air from the clean side, or wash with cooler cleaner. |
| Oil filter element clogged |
High oil filter differential pressure indication (Intellisys) or filter service hours exceeded. |
Replace oil filter element. |
| Thermostatic (temperature control) valve faulty |
Oil cooler stays cold while airend runs hot – valve element stuck in bypass. |
Replace thermostatic valve element. |
| Oil stop valve not opening |
Solenoid coil not energized or burnt; diaphragm cracked or aged. |
Check coil voltage; replace coil or diaphragm/valve. |
| Cooling fan damaged or fan motor failed |
Fan not turning, reduced airflow, unusual vibration. |
Repair/replace fan or motor; check fan thermal overload. |
| Discharge air ducting restricted (high back-pressure) |
Check for closed dampers, dirty louvres, excessive duct length or bends. |
Clear restriction; keep duct back-pressure within manufacturer limits. |
| Ambient temperature above rating |
Compare compressor room temperature to the unit's rating (standard 38 °C or high-ambient 46 °C). |
Improve room ventilation, add exhaust fans or ducting. |
| Temperature sensor fault (Intellisys units) |
Compare displayed value with an independent thermometer on the airend discharge pipe. |
Replace temperature sensor. |
| Temperature gauge fault (relay-controlled units) |
Verify with an independent thermometer. |
Replace gauge. |
Fault 2: High Oil Consumption or Excessive Oil Carryover in Compressed Air
In a healthy unit, oil carryover should be 3 ppm or less. One of the following is indicated by oily air, regular topping-up or oil at the drain points downstream.
| Possible Cause |
How to Check |
Fix |
| Coolant overfilled |
Check level with the unitrunning loaded– it should not be above the midpoint of the sight glass. |
Drain to correct level. |
| Scavenge (oil return) line blocked |
Sight glass in scavenge line (if fitted) shows no flow; orifice or strainer blocked. |
Clean orifice and strainer; blow through line. |
| Scavenge tube incorrectly positioned |
Tube must sit just above the bottom of the separator element (typically a few millimetres) per the service manual. |
Reposition tube to correct clearance. |
| Discharge pressure too low during operation |
Running below the mini pressure valve setting (roughly 3.5–4 bar / 50–60 psi) reduces separator efficiency. |
Correct pressure setting; repair mini pressure valve; reduce excessive air demand. |
| Separator element damaged or saturated |
High separator differential pressure, or visible tears/holes on the element. |
Replace separator element and gaskets. |
| Internal baffle in separator tank damaged |
Sudden increase in carryover, heavy oil on element exterior. |
Inspect tank internally; repair or replace. |
| External oil leaks |
Oil traces around fittings, seals, cooler, drain valve. |
Tighten fittings, replace seals or gaskets. |
Fault 3: Low System Pressure
| Possible Cause |
How to Check |
Fix |
| Air demand exceeds compressor output |
Unit runs fully loaded continuously but pressure still falls. |
Reduce demand, fix downstream leaks, or add capacity. |
| Blowdown valve not closing when loaded |
Continuous air venting from blowdown silencer while the unit is loaded. |
Repair or replace blowdown valve. |
| Inlet valve not opening fully |
Check butterfly/piston movement and linkage during loading. |
Clean, repair or replace inlet valve. |
| Loading cylinder (unloader cylinder) fault |
Cylinder not stroking; leaking piston seals. |
Rebuild or replace cylinder. |
| Load solenoid valve (1SV) fault |
No click when energized; blocked port or burnt coil. |
Clean, replace coil or valve. |
| Leaks in customer pipework |
Pressure drops quickly after unit unloads or stops. |
Leak survey and repair. |
| Pressure set point too low |
Check offline/online pressure settings. |
Adjust settings within rated pressure. |
| Pressure sensor fault (Intellisys units) |
Compare displayed pressure with a calibrated gauge. |
Replace pressure transducer. |
| Pressure gauge or pressure switch fault (relay-controlled units) |
Compare with a calibrated gauge; check switch differential. |
Replace gauge or switch. |
| Sensing line leaking |
Inspect hose from separator tank to sensor/gauge/switch. |
Replace hose and fittings. |
Fault 4: Discharge Pressure Too High
Over-pressure is usually a control fault– the unit is not unloading when it should. If the safety relief valve lifts, stop the unit and find the cause.
| Possible Cause |
How to Check |
Fix |
| Inlet valve not closing |
Valve stuck open due to dirt or worn seals. |
Clean or rebuild inlet valve. |
| Loading cylinder fault |
Cylinder not returning inlet valve to closed position. |
Rebuild or replace cylinder. |
| Load solenoid valve (1SV) stuck |
Valve remains energized/open. |
Clean or replace valve. |
| Pressure set point too high |
Check controller or pressure switch settings. |
Reset to correct value. |
| Pressure sensor fault (Intellisys) |
Compare with calibrated gauge. |
Replace transducer. |
| Pressure gauge or switch fault (relay-controlled units) |
Compare with calibrated gauge; switch not opening at set pressure. |
Replace switch/gauge. |
Fault 5: High Running Current or Trip During Operation
| Possible Cause |
How to Check |
Fix |
| Supply voltage too low |
Measure voltage at terminals under load; check for imbalance between phases. |
Correct supply issue; check cable sizing. |
| Loose wiring or terminals |
Thermal imaging or visual inspection for discoloured terminals. |
Retighten connections. |
| Unit running above rated pressure |
Compare discharge pressure with nameplate rating. |
Lower pressure setting. |
| Separator element blocked |
High separator differential pressure (> about 1 bar / 15 psi). |
Replace separator element. |
| Main contactor fault |
Burnt or pitted contacts, contactor chatter. |
Replace contactor. |
| Airend fault |
Abnormal noise, high vibration, metal particles in oil. |
Airend inspection/overhaul. |
| Main motor fault |
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