Compressor Won’t Build Up to Pressure
Your Compressor Is Running… But the Pressure Gauge Isn’t Climbing
If your compressor runs continuously but never hits the pressure it’s supposed to, something’s wrong. This is different from low discharge pressure: in this case, the unit just can’t reach cut-out, no matter how long it runs. Whether you're using a reciprocating, portable rotary screw, or stationary rotary screw compressor, here’s how to get to the bottom of it.
If You Have a Reciprocating or Portable Rotary Screw Compressor
These units should reach their max PSI and shut off once the tank is full. If they don’t, the issue is often mechanical or a sign of something leaking/stuck open.
Common Causes:
- Air Leaks – A cracked hose, leaky fitting, or open drain valve can cause air loss faster than the unit can build it.
- Faulty Check Valve – If air is bleeding back into the pump or motor, pressure won’t climb.
- Stuck Open Unloader Valve – This prevents full pressure from building during run cycles.
- Damaged Pistons or Valves (Recip Models) – Worn internals mean reduced compression power.
- Misadjusted Pressure Switch – The unit may never see the cut-out setpoint if it’s set too high.
What You Can Do:
- Use soapy water to find leaks—especially around tank fittings, couplers, and hoses.
- Inspect or replace the check valve and unloader valve.
- Review and reset the pressure switch to manufacturer specs.
- For air-cooled reciprocating compressors, listen for weak compression strokes or "puffing" sounds: signs of valve or ring wear.
If You Have a Stationary Rotary Screw Compressor
In a rotary screw system, the compressor should build to a set pressure and modulate or unload. If it runs nonstop and can’t hit target pressure, the problem is more likely internal or system-wide.
Likely Issues:
- External Air Leaks – Downstream demand may be pulling more air than the compressor can make.
- Inlet Valve Not Fully Opening – A stuck or slow inlet valve limits air intake and overall flow.
- Load Solenoid Failure – If the solenoid doesn't trigger full load, the machine stays in idle or partial compression.
- Air end Wear or Rotor Damage – Loss of efficiency at the source = loss of pressure everywhere else.
- Improper Pressure Setpoints – The controller might be using outdated or miscalibrated targets.
Steps to Fix It:
- Audit your system for leaks and excessive air usage during runtime.
- Test inlet valve actuation and verify it's opening under full load conditions.
- Test or replace the load/unload solenoid valve.
- Inspect the air end if the machine has high hours or reduced performance.
- Review controller settings and pressure targets, then compare to OEM specs.
Prevent This From Happening Again
For Reciprocating and Portable Compressors
- Perform leak checks monthly, especially after transport or relocation.
- Inspect valves and replace your check valve annually if used daily.
- Log runtime cycles and catch signs of extended run time early.
For Stationary Rotary Screw Compressors
- Check inlet and solenoid valve performance during PM visits.
- Review controller settings regularly, especially after service calls.
- Track pressure trends. If you're running longer to hit the same PSI, inspect the air end.