6: Maintenance
ShopTek™ ST4, ST5, ST7, ST11, ST15 Three-phase 60 Hz User Manual
88292018-236 R00
52
Subject to EAR, ECCN EAR99 and related export control restrictions.
Compressor cannot pro-
duce full discharge pres-
sure
Air demand too high
Check service lines for leaks or open
valves.
Dirty air filter
Replace filter.
Inlet valve bleed orifice obstructed/
plugged
Check the control line bleed orifice
inside the inlet valve for blockage or
obstructions.
Defective unload solenoid valve
Check the valve - if it does not operate
when energized, replace the valve coil
or the entire valve if defective.
Minimum pressure valve malfunc-
tion
Repair or replace minimum pressure
valve
Pressure sensor malfunction
Check connection and sensor –
replace if sensor is defective.
Belts slipping due to lack of tension
Check belts. Re-tension or replace as
necessary.
Line pressure rises above
unload pressure set-point
Control system leak causing loss of
pressure signals
Check for leaks.
Inlet valve stuck open
Remove the intake hose and check the
inlet valve for proper operation.
Defective unload solenoid valve
Check the valve for proper operation -
open when energized - replace if nec-
essary
Plugged/obstructed control line
strainer
Clean or replace strainer
Pressure sensor malfunction
Check connection and sensor –
replace if sensor is defective.
High compressor fluid con-
sumption
Clogged return line or orifice
Clean or replace the strainer.
Separator element damaged or
malfunctioning
Change separator.
Lubrication system leak
Check all pipes, connections, and com-
ponents.
Excess fluid foaming
Drain fluid and change.
Fluid level too high
Drain and change - check that the com-
pressor temperature has not dropped
below 170ºF (76.7ºC).
Pressure relief valve opens
frequently
Pressure relief valve defective
Replace.
Plugged/obstructed separator
Check separator differential.
Pressure sensor malfunction
Check connection and sensor - replace
if sensor is defective.
Table 6-3: Troubleshooting guide
Symptom
Probable cause
Remedy
