15
Maintenance
Troubleshooting
PROBLEM
POSSIBLE CAUSE
SOLUTION
PUMP RUNNING
NORMALLY
BUT PRESSURE
LOW ON
INSTALLATION
Pump sucking air
Check water supply and possibility of air.
Check valves sticking
Check and clean or replace if necessary.
Unloader valve seat faulty
Check and replace if necessary.
Nozzle incorrectly sized
Check and replace if necessary.
Worn piston packing
Check and replace if necessary.
FLUCTUATING
PRESSURE
Valves worn
Check and replace if necessary.
Blockage in valve
Check and clean if necessary.
Pump sucking air
Check water supply connections.
Worn piston packing
Check and replace if necessary.
Insufficient water
Check filter and hose for breakage.
PRESSURE
LOW AFTER
PERIOD OF
NORMAL USE
Nozzle worn
Check and replace if necessary.
Suction or delivery valves worn
Check and replace if necessary.
Suction or delivery valves blocked
Check and clean if necessary.
Unloader valve seat worn
Check and replace if necessary.
Unloader adjusted improperly
Call local Karcher dealer. Tampering with the
factory setting may cause personal injury and/or
property damage and will void the manufacturer's
warranty.
Worn piston packing
Check and replace if necessary.
Bypass valve within unloader is
obstructed or leaking
Remove and clean bypass cartridge.
PUMP
NOISY
Air in suction line
Check water supply and connections on suction
line.
Broken or weak suction or delivery
valve spring
Check and replace if necessary.
Foreign matter in valves
Check and clean if necessary.
Worn bearings
Check and clean if necessary.
Excessive temperature of water
Reduce to below 140°F.
PRESENCE OF
WATER IN
PUMP OIL
Oil seal worn
Check and replace if necessary.
High humidity in air
Check and change oil twice as often.
Piston packing worn
Check and replace if necessary.
WATER DRIPPING
FROM UNDER PUMP
Piston packing worn
Check and replace if necessary.
O-Ring plunger retainer worn
Check and replace if necessary.
OIL DRIPPING
FROM PUMP
Oil seal worn
Check and replace if necessary.
EXCESSIVE
VIBRATION IN HIGH
PRESSURE HOSE
Irregular functioning of the pump
valves
Check and replace if necessary.
Obstruction in filter
Clean inlet filter.
MOTOR WILL
NOT RUN
Motor overload
Push in the overload button located on the motor
(single phase) or the overload button
on the magnetic start switch (three phase).
Step down transformer fuses
Check fuses and voltage. Replace if necessary.
Coil of magnetic starter defective
Replace coil after the timer and unloader
switch have been tested.
MACHINE WILL
NOT TURN ON
WHEN SWITCH
IS PUSHED
Timer is defective
Join wires 15 and 16 together on timer.
If machine works, replace timer.
Karcher HD 300-310 Operator’s Manual 9.800-086.0 - P
