Case Magnum 7210, Сервисный бюллетень

Страница: 18 / 26

Service Bulletin NTR SB 026 96
Magnum Hitch Diagnostic Codes and Service Manual update
Page 18 of 26
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HITCH VALVE COMPONENTS AND FUNCTION CONTINUED
Control spool
Raise -
Once the control spool is shifted to the right it then directs PFC pump pressure to the left
end of the lockout plunger spool (the lockout spool dose not move) but the pressure in that area
will unseat the load check poppet to raise the hitch.
Lower
-
Once The control spool is shifted to the left it then directs PFC pump oil to the right end
of the lockout plunger spool which (unseats) pushes the lock check poppet to the left to lower the
hitch.
- If the control spool stick in the center position the hitch won’t raise or lower.
- if the control spool sticks to the left, the hitch will drift down.
- If the control spool sticks to the right, the hitch will drift up.
Lockout plunger spool
Raise
-
The lockout plunger spool is not shifted or moved with oil pressure when the hitch is
raised. The piston pump oil pressure at the left end of the spool will unseat the load check poppet
to raise the hitch.
Lower - The lockout plunger is shifted to the left with piston pump pressure. The lockout spool
pushes the load check poppet to the left to lower the hitch.
- If the lockout plunger spool sticks to the right, the hitch won’t lower.
-
If the lockout plunger spool sticks to the left the hitch will settle.
Load check poppet
The load check poppet prevents the hitch from settling when the engine is turned “off” or when
the hitch valve is in neutral (solenoid not powered by hitch control module).
The load check plunger must shift to the left for the hitch to raise or lower.
- If the load check poppet sticks to the left the hitch will settle.
Signal check valve
The hitch signal check valve isolate the piston pump signal circuit from the Steering valve, remote
valves and the power beyond valve. The PFC pump pressure will be set by the valve producing
the highest signal pressure.