070.250-IOM (APR 11)
Page 21
408 MM ROTARY SCREW COMPRESSOR
MAINTENANCE
TROUBLESHOOTING THE 408 MM COMPRESSOR
SYMPTOM
PROBABLE CAUSES and CORRECTIONS
SLIDE VALVE and/or SLIDE STOP
WILL NOT MOVE
4-way hydraulic control valve failed.
Repair or replace.
Slide stop indicator rod stuck.
Contact Johnson Controls–Frick Service for assistance.
Check both S.V. and S.S. feedback devices for wiring and resistance.
Compressor must be running with sufficient oil pressure.
Unloader piston stuck.
Contact Johnson Controls–Frick service for assistance.
Piston Seals worn out or damaged.
Contact Johnson Controls-Frick Service for
assistance.
NOTICE
Unless the Service Technician has been certified by Johnson Controls–Frick to rebuild our compressors,
troubleshooting the compressor is limited to identifying the probable cause. If a mechanical problem is suspected,
contact Johnson Controls–Frick Service. DO NOT ATTEMPT TO DISASSEMBLE COMPRESSOR.
TROUBLESHOOTING THE HYDRAULIC SYSTEM
SYMPTOM
PROBABLE CAUSES and CORRECTIONS
SLIDE VALVE WILL NOT LOAD OR
UNLOAD
Solenoid coils burned out.
Replace.
Valve closed.
Open hydraulic service valves.
Solenoid spool stuck or centering spring broken.
Replace.
Check LED on coil. If lit, there is power to the coil.
Check coil.
Solenoid may be actuated mechanically by inserting a piece of 3/16” rod against
armature pin and pushing spool to opposite end. Push A side to confirm unload
capability. If valve works, problem is electrical.
SLIDE VALVE WILL LOAD BUT
WILL NOT UNLOAD
A side solenoid coil may be burned out.
Replace.
Dirt inside solenoid valve preventing valve from operating both ways.
Clean.
Check LED on coil. If lit, valve is functioning mechanically. Problem is electrical.
Solenoid may be actuated mechanically by inserting a piece of 3/16” rod against
armature pin and pushing spool to opposite end. Push A side to confirm unload
capability. If valve works, problem is electrical.
SLIDE VALVE WILL UNLOAD BUT
WILL NOT LOAD
A side solenoid coil may be burned out.
Replace.
Dirt inside solenoid valve preventing valve from operating both ways.
Clean.
Check LED on coil. If lit, valve is functioning mechanically. Problem is electrical.
Solenoid may be actuated mechanically by inserting a piece of 3/16” rod against
armature pin and pushing spool to opposite end. Push A side to confirm unload
capability. If valve works, problem is electrical.
SLIDE STOP WILL NOT FUNCTION
EITHER DIRECTION
Solenoid coils may be burned out.
Replace.
Solenoid service valves may be closed.
Open.
Manually actuate solenoid. If slide stop will not move, mechanical problems are
indicated.
Consult Johnson Controls-Frick Service.
