Troubleshooting Solenoid Valves
Tech Talk 04/12/00
Table of Contents
Symptom: Solenoid Failures
- If voltage will not complete the stroke of AC current solenoid, it will
burn out the coil.
- Signal simultaneously transmitted to both solenoids of a double-solenoid
valve. One or both solenoids will be unable to complete their stroke
and will burn out. Interlock the electrical signal for
prevention.
- Covers left off solenoids will allow cast iron dust or other metallic
chips to collect within the magnetic field. Plunger cannot complete
stroke and solenoid burns out or contamination could enter the field via
the push pin. The wet armature solenoid uses a sealed tube assembly;
does not contaminate the fluid.
- Push rod peens to a point where it is not long enough to actuate the
valve. Replace with new pin.
- Mechanical damage to leads and coils (short circuit, open connections,
open windings, etc.)
- Tight spool or other mechanical valve parts being actuated can prevent
the solenoid from completing its stroke, leading to burnout.
- Replacement springs too heavy in valve; overloads solenoid and shortens
life.
- Wrong voltage or frequency either prevents operation due to inadequate
load-handling capacity with lower voltage, or burns out of the coil due to
improper winding and excessive voltage.
- Dirty contacts may not supply sufficient current to solenoid to satisfy
inrush demands.
- Low-voltage, direct-current solenoids may be affected by low-battery
capacity on cold mornings directly after starting cold engine.
- Long feed lines to low-voltage solenoids ma cause erratic operation.
- High ambient temperature or confined area -- heat not dissipated
properly.
Symptom: Solenoid Valve Fails to Operate
- Is there electrical signal to the solenoid or operating device?
- Is the solenoid push rod shifting the pilot spool far enough?
- If the supply to the pilot body is orificed, is the orifice restricted?
- Has foreign matter jammed the main spool?
- Is pilot pressure available? Is pilot drain restricted?
- Is pilot tank port connected to main tank port where pressured are high
enough to neutralize pilot input pressure?
- Are solenoids improperly interlocked so that a signal is provided to
both units simultaneously?
- Has mounting pad been warped from external heating or improper bolt
torque?
- Is fluid media excessively hot?
- Is there foreign matter in the fluid causing gummy deposits?
- Is an adequate supply of fluid
- being delivered to actuate the load?
- Check circuit for possible interlocks on pressure sources to valve or
pilot.
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