Low Or Fluctuating Output - Graco Magnum L10 Repair Manual

Specific Problem
Pump cycles, but output is low or
surging.
332642C

Low or Fluctuating Output

Cause
See Basic Troubleshooting,
page 15.
Worn or obstructed inlet and
outlet valves.
Prime/Spray valve is leaking out
drain line when Prime/Spray
valve is in SPRAY position.
Voltage from electrical outlet is
too low. Low voltages reduce
sprayer performance.
Extension cord is too long or not
heavy enough gauge.
Leads from motor or pressure
switch to control board are
damaged, loose, pinched, or
overheated.
Motor brushes are worn.
Motor brush springs are broken. If springs are broken, replace motor using Motor Kit.
Motor brushes are binding in
brush holders.
Motor stops before sprayer
reaches correct pressure (stall
pressure is too low).
Control board is damaged.
CAUTION: Do not perform
control board diagnostics until
you have determined the
armature is good. A damaged
armature can burn out a good
control board.
Solution
Check for worn pump valves as follows:
Prime sprayer with paint. Turn the Prime/Spray
valve to SPRAY position. Turn pressure control fully
clockwise.
Trigger spray gun briefly.
When spray gun trigger is released pump should
cycle momentarily and stop.
If pump continues to cycle, pump valves may be
worn or obstructed.
For replacement inlet and outlet valve kits, see List
of Kits, page 30.
Check Prime/Spray valve for debris trapped on seat
and for worn parts. Torque to 130 - 180 in-lb
(15.8 - 18.1 N•m). Replace if parts are worn using
Prime/Spray Valve Kit. See List of Kits, page 30.
Check voltage of outlet. Meter must read 220-240
VAC.
Replace extension cord.
See Grounding and Electrical Requirements,
page 12.
Be sure terminals are centered and firmly
connected. Inspect for pinched wiring and wiring
insulation and terminals for signs of overheating.
Replace any loose terminals or damaged wiring.
Securely reconnect terminals.
Check length of BOTH brushes (brushes do not
wear evenly on both sides of the motor). Brush
length must be 0.25 in. (6.4mm). If brushes are
worn, replace motor using Motor Kit. See List of
Kits, page 30.
See List of Kits, page 30.
Clean brush holders. Remove carbon dust with
small cleaning brush.
Replace pressure control using Pressure Control
Switch Kit, page 28.
See Control Board Diagnostics, page 29. If
damaged, replace control board using Control
Board Kit. See List of Kits, page 30.
Advanced Troubleshooting
25