Graco Mark IV 249636 Operation - Repair - Parts page 24

Electrical
Symptom: Sprayer does not run or stops running
• Plug sprayer into correct voltage, grounded outlet
• Set power switch OFF for 30 seconds and then ON
again. This ensures sprayer is in normal run mode.
• Turn pressure control knob clockwise 1/2 turn.
• View digital display
DIGITAL CONTROL BOARD
DISPLAY STATUS LIGHT
Blank Never lights
---- psi Blinks once and
stops
24
Relieve pressure; page
19.
INDICATION
No power to control
No RUN command to
control board
To avoid electrical shock or moving parts hazards when
covers are removed for troubleshooting, wait 30 sec-
onds after unplugging power cord for stored electricity to
dissipate. Keep clear of electrical and moving parts dur-
ing
troubleshooting procedures.
• If no digital display is available, use control board
status light to troubleshoot problems: Turn ON/OFF
switch OFF, remove control cover and then turn
power back ON. Observe status light.
WHAT TO DO
1 Verify required voltage is present
2 Check wiring connections to control board
3 Perform continuity check on power cord and switch.
Replace power cord or switch as needed.
4 If steps 1 - 3 are ok, replace control board
1 Make sure prime valve is open and there is no pressure in
the system
2 Turn pressure control knob clockwise
3 Check potentiometer connection to control board
4 Check pressure control knob alignment to potentiometer
shaft. Turn shaft fully clockwise and attach knob in full ON
position.
5 Unplug potentiometer. Short out center pin of control board
potentiometer connector to each outer pin (one at a time).
If sprayer runs, replace potentiometer, page 44.
6 Check transducer connection
7 Disconnect and reconnect transducer plug to ensure good
connection with control board socket. Check that
transducer contacts are clean.
8 Open prime valve. Connect a known good transducer in
place of the sprayer transducer. Set sprayer ON. Replace
transducer If sprayer runs. Replace control board If sprayer
does not run.
Troubleshooting
311287A