6: Maintenance
SN55, SN55S, SN55V, SN75, SN75S, SN75V User Manual
02250247-571 R04
75
Subject to EAR, ECCN EAR99 and related export control restrictions.
Compressor shuts
down with air demand
present
Loss of control voltage
Check power supply for 24V DC output.
Replace power supply if necessary.
Low incoming voltage
Consult power company.
Excessive operating pressure
Reset. If trouble persists, check that line pres-
sure does not exceed maximum operating pres-
sure of the compressor (specified on
nameplate).
Separator requires mainte-
nance indicated by STS Con-
troller™
Replace separator.
Machine programmed for
wrong pressure setting
Reprogram using STS Controller.
Defective regulator valve
Regulator valve should cause inlet valve to
close when the pressure switch contacts open.
Repair if defective.
Defective blowdown valve
Blowdown valve should exhaust separator/
sump tank pressure to 18 psig (1.2 bar) when
maximum operating pressure is reached.
Repair if defective.
Cooling water temperature too
high
Reduce water temperature to 85°F (29.4°C) or
less. Water-cooled only.
Cooling water flow insufficient
Check water lines and valves (water-cooled
only).
Cooler plugged
Clean tubes. If plugging persists, install water
conditioner (water-cooled only).
Cooling air flow restricted
Clean cooler and check for proper ventilation.
Ambient temperature is too
high
Provide sufficient ventilation.
Low fluid level
Add fluid.
Clogged filter
Change the fluid filter element.
Thermal valve not functioning
properly
Replace element.
Water flow regulating valve not
functioning properly
Change (water-cooled only).
Compressor will not
build full discharge
pressure
Air demand is too great
Check service lines for leaks or open valves.
Dirty air filter
Check the filter indicator and inspect and/or
change element if required.
Inlet valve bleed orifice
plugged
Ensure control line bleed orifice located inside
inlet valve is not plugged.
Pressure regulator out of
adjustment
Adjust regulator according to control adjust-
ment instructions in the Maintenance section.
Defective pressure regulator
Replace regulator.
Defective unload solenoid
valve
Check that the valve closes when energized.
Replace the coil or the complete valve if defec-
tive.
Symptom
Probable cause
Remedy
