Throubleshooting - Danfoss MCV105C Manual

PUMP NEUTRAL ADJUSTMENT (continued)
3. Disconnect the electrical line at the connector.
4. Start the prime mover and run at low idle.
5. Warm the system up for several minutes to bleed air.
6. Slowly increase the prime mover speed to rated rpm.
7. Slowly rotate the neutral adjustment screw, with a 5/32"
Allen wrench, until the pressure is equal in both servo
gauges.
8. Slowly rotate the neutral adjust screw until one of the
servo gauges starts to increase in pressure.
9. Slowly rotate the neutral adjust screw in the opposite
direction until the other servo gauge begins to increase in
LOCATION, SERVO GAUGE PORT
Location of one of the servo gauge ports on the pump.
TROUBLESHOOTING FAILURE MODES
A. NO PUMP OUTPUT
1. Check voltage or current supply to the pilot stage.
If faulty, check the electrical system. If fine:
2. Check the coil resistance in the pilot at the input
connector to the pilot. The resistance across the
two Pins (A and B) should be 23 ohms for single coil
pilots. For dual coil pilots, resistance is 20 ohms
across A and B and 16.5 ohms across C and D. If
resistance is infinite across either coil, the pilot
should be replaced.
3. Jog the manual operator on the top of the pilot. If the
hydraulic system does respond, the failure must be
an electrical problem. If there is no response, check
© Danfoss, 2014-05
10. Turn the neutral adjust screw back one half the amount
11. Hold the neutral adjust screw and torque the lock nut to
12. Stop the prime mover.
13. Reconnect the electrical line.
14. Run the system briefly to ensure that it operates propor-

THROUBLESHOOTING

The MCV105C EDC is one component in a control system.
When the system fails, check the most obvious failure modes
first. Is the battery fully charged? Is there a hydraulic leak
somewhere? Are all connections tightly fastened? Are O-
rings in place?
When a process of elimination indicates that the system
problem may reside in the EDC, the failure mode is likely to
be one of the following six.
.4375–20 SAE STR
THR O-RING BOSS
SERVO PRESSURE
GAUGE PORT
(2) PLACES
Electrical actuation of the valve and/or hydraulic jogging
of the valve may cause pump output and movement by
the driven machine. Take precautions to ensure that no
personnel are in a position to be injured by the machine
1357
if it should move.
B. THE PUMP CANNOT BE NULLED OR CREEPS
11152452 • Rev AA • May 2014
pressure. Note the amount the neutral adjust screw was
turned in this step.
turned in Step 9.
25-30 in.-lbs.
tionally on both sides of the null command. Swashplate
movement can be verified by watching movement of the
swashplate feedback shaft, see Dimensions, page 6.
WARNING
the service filter in the casting for the possibility of
damage or plugging. See Dimensions, page 6. If
the filter is dirty, replace it. If it is clean, replace the
pilot.
SLOWLY IN ONE DIRECTION
1. Replace the pilot with a spare. If the problem is
solved, the pilot is faulty. If the problem is not
solved, unbolt the second stage from the pump and
check the spool and sleeve for contamination or
damage. If cleaning these parts clears up the
problem there is a filtration problem. Check the
charge pump filter and change pump oil.
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