Graco Pro 455 Repair Manual page 16

Digital Display Messages
No display does not mean that sprayer is not pressurized. Relieve pressure before repair; page 4.
DISPLAY
No Display Sprayer stops. Power is not applied.
Sprayer may be pressurized.
Sprayer is pressurized. Power is ap-
psi
plied. (Pressure varies with tip size and
bar
MPa pressure control setting.)
Sprayer may continue to run. Power is
applied.
Sprayer stops. Power is applied.
Sprayer stops. Power is applied.
Sprayer stops. Power is applied.
Power is applied.
Pressure Control Transducer
Removal
Refer to Fig. 7, 8 or 9 depending on sprayer voltage.
1.
Relieve pressure; page 4.
2. Remove four screws (18) and cover (39).
3. Disconnect lead (E) from motor control
board (35).
4. Remove two screws (22) and filter housing (45).
5. Thread transducer lead plastic connector down
through transducer grommet (28).
6. Remove pressure control transducer (52) and
packing o-ring (51) from filter housing.
Installation
1. Install packing o-ring (51) and pressure control
transducer (52) in filter housing (45). Torque to
30–35 ft-lb.
2. Thread transducer lead plastic connector up
through transducer grommet (28).
3. Install filter housing (45) with two screws (22).
16
309056
Pressure Control Repair
SPRAYER
OPERATION
INDICATION
Loss of power
Normal operation
Pressure greater than
4500 psi (310 bar, 31 MPa)
Pressure transducer faulty,
bad connection or broken
wire.
Line voltage too high
Too much current
Pressure less than
200 psi (14 bar, 1.4 MPa)
4. Connect lead (E) to motor control board (35).
5. Install cover (39) with four screws (18).
Pressure Adjust Potentiometer
Removal
Refer to Fig. 7, 8 or 9 depending on sprayer voltage.
1.
2. Remove four screws (18) and cover (39).
3. Disconnect all leads from motor control board (35).
4. Remove five screws (36) and board (35)
5. Remove potentiometer knob (27), sealing shaft nut
(33) and pressure adjust potentiometer (26).
Installation
1. Install pressure adjust potentiometer (26), sealing
shaft nut (33) and potentiometer knob (27).
a. Turn potentiometer fully clockwise.
b. Install knob at full clockwise position.
2. Install board (35) with five screws (36).
3. Connect all leads to motor control board (35).
4. Install cover (39) with four screws (18).
ACTION
Check power source. Relieve
pressure before repair or dis-
assembly.
Spray
Replace pressure control
board
Check transducer connection.
Open drain valve. Substitute
new transducer for transducer
in sprayer. If sprayer runs, re-
place transducer.
Check for voltage supply
problem
Check for locked rotor,
shorted wiring or motor. Re-
pair or replace failed parts.
Increase pressure if desired.
Drain valve may be open
Relieve pressure; page 4.