Fluid Pump Runs Constantly - Graco Express 3900 Operation

Troubleshooting

Fluid Pump Runs Constantly

Troubleshooting Procedure:
With a pressure gauge plumbed into the paint
hose, start the engine. Turn pump switch ON.
Does sprayer exceed maximum pressure?
YES
Disconnect clutch wires from control board (see
diagram, page 18). Does the pump stop run-
ning?
YES
Make sure clutch wires are plugged in (see dia-
gram, page 18). Do the clutch test points read
10-18 DC volts?
YES
Unplug transducer from control board.
YES
Bad transducer.
Replace and test with a new one.
16
1. Perform Pressure Relief Procedure, page 7, turn
prime valve forward to SPRAY position, and turn
power switch OFF.
2. Remove control box cover.
Pump problem. See the proper fluid pump
manual for the sprayer for further trouble-
NO
shooting procedures.
Mechanical problem in the clutch pinion as-
NO
sembly (clutch may be close to the rotor).
Check for a short from the two clutch wires
NO
to the frame. If shorted, repair or replace
faulty wire.
Replace the control board.
NO
334121B