U1, U2; Operation; Functional Description; Repair - Danfoss 51 Series Service Manual

Service Manual

U1, U2

Operation

Repair

Series 51 Two Position Controls Service Manual

Functional Description

The U* two-position controls consist of a ported housing containing a shuttle spool and a solenoid. The
shuttle spool resolves which port, system A or system B, is at higher pressure, routing that high pressure
to the four-way valve to power the servo piston. The solenoid actuates the four-way valve causing the
motor to shift displacement. The sensing piston functions only as a push-rod in this control.
The motor defaults to minimum displacement, shifting to maximum when the solenoid operates.
Optional orifices at locations T1, T2, T3, T7, and T8 control shift speeds.
This table shows control logic, input voltage, and connector options for each control type.
Control logic, input voltage and connector options
Type SOL on
U 1 max.
2 max.
Schematic diagram
L2
X
A
X
X
U5
B
L1
The PCOR option is not available with U1/U2 controls.

Disassembly

1. Using a 1/4 inch internal hex wrench, remove plugs (M16, N20, NT40). Remove and discard O-rings
(M16A, 20A, NT40A).
2. Remove shuttle spool (NT42).
3. Using a 3mm internal hex wrench, remove plug (N26).
4. Using a 1/8 inch internal hex wrench, remove plug (M18). Remove and discard O-ring (M18A).
5. Remove coil nut and coil from solenoid (M1).
6. Using a thin 3/4 inch hex wrench, remove cartridge (M1) from control. Keep the pushrod in the
cartridge.
7. Remove screws (M22) and washers (M24).
8. Remove control housing (M10). Remove and discard O-rings (G36, G38, G42) or gasket (G420).
11009442 • Rev CA • January 2015
SOL off
min.
min.
M4 M3
X X
M1
X
max.
disp.
T2
)( )(
T3
T7
)(
T8
T1
)(
X3(M5)
M2
X
P101 214E
Volts Connector
12v DIN 46350
24 v DIN 46250
39