The Five Problems You Will Encounter
Pneumatic systems are simple and reliable, but when something goes wrong, it is frustrating. Most problems fall into one of five categories, and most are fixable without calling an engineer.
Problem 1: Low or Fluctuating Pressure
What you notice:
– Compressor runs constantly but pressure stays low
– Pressure creeps up slowly
– Pressure fluctuates during operation
Leak in the System: Apply soapy water to all connections and look for bubbles. Even tiny leaks add up.
Fix:
– Tighten loose connections (turn 1/4 turn at a time)
– Replace cracked hoses
– Swap out worn fittings
If you are constantly tightening the same connection, the fitting threads are failing. Replace it with a quality Parker or PCL fitting—do not keep band-aiding it.
Faulty Check Valve: The one-way valve inside the compressor head prevents backflow.
Signs:
– Pressure builds very slowly even though motor is running
– Motor sounds normal but just cannot reach target pressure
– Motor runs hot
Fix: If it is a bolt-on check valve, they are replaceable (£20-50). If internal, the pump probably needs rebuilding.
Tank Pressure Loss Overnight: Your tank holds pressure but very slowly leaks over hours.
This is often the tank itself—pinhole rust corrosion.
Problem 2: Tools Underperform
You press the trigger and the impact wrench barely turns, or the spray gun sputters.
Likely cause: Inadequate pressure reaching the tool.
Before troubleshooting the tool, confirm system pressure is where it should be. Use a separate pressure gauge on the main line.
Blocked or Clogged Filter: Water, dirt, or debris in the filter reduces air flow.
Signs:
– Pressure gauge shows normal, but tools are weak
– Hissing sound from the tool (back-pressure)
Fix:
– Locate the filter (usually mounted before the regulator or on the tool line)
– Check the element—if it is dark or wet, it is clogged
– Replace the element (not expensive, £10-20)
Problem 3: Water or Oil in the Air
You notice liquid on tools or in the outlet, or spray guns produce speckled finishes.
What is happening: Compressed air becomes humid inside the tank. When cooled in the line, water condenses.
Immediate: Drain the tank completely using the petcock at the bottom. Drain any water traps in your system.
Long-term: Install an aftercooler (removes 80%+ of moisture before it reaches the tank). Install water traps before precision tools (spray guns especially).
Quality water management products from Festo and ASCO cost £50-200 but prevent tool damage that would cost far more.
Problem 4: Hissing Sounds or Constant Air Leaks
The system is pressurised and air is escaping somewhere.
Hissing from the regulator: Tighten the cap nut on top (usually 13mm wrench). If it still hisses, the seal is worn and the regulator needs replacement.
Hissing from a connection: Spray with soapy water to confirm location. Turn off, depressurize, apply new PTFE tape to the male thread. Reassemble and re-pressurize.
Hissing from the solenoid valve: This is normal in tiny amounts (a whisper). If it is loud, the valve seal is failing and the valve needs replacement.
Problem 5: Tools Wont Turn On or Pneumatic Solenoid Wont Trigger
The compressor runs, pressure is there, but tools do not activate.
Likely cause: Solenoid valve is stuck or the control signal is not reaching it.
Test:
– Turn off the compressor
– Listen near the solenoid valve (usually small cylinder on the tool line)
– Trigger the tool
– You should hear a distinct click when it energizes
No click = solenoid is not getting power. Check:
– Is the tool plugged in?
– Is the cord intact?
– Is the power outlet working?
Fix: If you hear the click but valve does not open, turn off compressor and depressurize. Gently tap the solenoid body with a rubber mallet (sometimes dislodges stuck plungers). If that does not work, solenoid needs replacement (usually £30-80 for a quality ASCO or Festo unit).
Preventive Maintenance
The best fix is preventing problems in the first place:
– Drain the tank weekly (or daily in humid weather)
– Check connections monthly with soapy water
– Replace hose every 5-7 years (even if it looks fine)
– Change oil regularly if using an oil-lubricated compressor
– Clean motor cooling fins monthly
Quality fittings and hoses from Parker, PCL, and John Guest fail less often and last longer than cheap alternatives.
Need Replacement Parts?
We stock everything: hoses, fittings, regulators, solenoids from Festo and ASCO, water traps, and filters. If you are debugging a system and need parts, we are here to help.
Call 01474 334537 or browse our components and spares online.
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