FLUID SYSTEM DIAGNOSTICS - Unloader
PROBLEM
POSSIBLE CAUSE
SOLUTION
Very low or no flow
Unloader stuck in bypass
Isolate the flow problem. If it occurs before the unloader discharge point, check the piston
assembly to see if it is fouled or stuck in bypass mode.
Unloader will not unload
Debris in unloader
Take bottom nut off unloader, identify ball, spring and seat. Clean out any debris and
Sever leak on the outlet of unit
Check for leaks and repair.
Unloader (flow) cycles with
system under pressure
Improper flow
Any variation in flow form what the orifice is sized can cause cycling. System must produce the
rated flow constantly.
Nozzle to small
A nozzle that is too small can cause the flow to be reduced.
Nozzle clogged
A distorted spray pattern indicates a clogged nozzle.
Improper unloader orifice
The systems rated output should indicate the proper sized orifice for your system.
Unloader orifice clogged
Check the orifice for clogs and clear out any debris.
Injector orifice clogged
If the system has a Venturi injector downstream of the unloader, check the orifice for clogs.
Other downstream restriction
Scale buildup can restrict flow. Check; controls, valves, switches, trigger gun, and lance.
Descale as necessary and begin preventive maintenance program for scale prevention.
Pump not delivering the rated
pressure
See low pressure or low flow diagnostics.
High water supply pressure
Check inlet water supply for excessive pressure.
Unloader (flow) cycles with
system in bypass
No restrictions on the unloader
Check unloader bypass port to see if a flow restrictor is properly installed. Install one if none is
present.
Downstream leakage (excessive)
Causes the unloader to since a continuing flow and divert it to the closed gun. Repair or replace.
Accumulator downstream (option) Remove the accumulator from the system.
Unloader (pressure)
produces smooth flow & low
volume
Unloader adjusted too low
Adjust the unloader using the pressure gauge for the correct pressure.
Spray nozzle clogged
A distorted spray pattern indicates a clogged nozzle.
Spray nozzle too small
A small nozzle causes a reduced flow and cycling may result.
Injector orifice blocked
If the system has a Venturi injector downstream of the unloader, check the orifice for clogs.
System not delivering rated flow
See flow diagnostics.
Unloader (flow) produces
smooth flow & low volume
Unloader adjusted too low
Adjust unloader and regulator until proper pressure is achieved.
Unloader valve stuck in bypass
If unloader is sticking, repair or replace as necessary.
Restriction in system
Downstream restrictions can cause a reduction in flow. Check; controls, valves, switches, trigger
gun, and lance. Descale as necessary and begin preventive maintenance program for scale
prevention.
