User Manual
36
PROBLEM CHECK THIS POSSIBLE CAUSE CORRECTIVE ACTION
Pump does not start Electrical power supply Controller plug disconnected Reconnect control plug to 
power outlet
Blown fuse or breaker tripped 
on overload
Determine cause and replace 
fuse or reset breaker
Pump Motor failure Replace pump
Sensors Defective sensors, sensor 
error
Check wiring continuity. 
Repair or replace
Pump starts, but cycles 
continuously
Differential controller On and/or off temperature 
differential set points too low
Reset on and off 
differentials according to 
recommendations
Piping Reversed connections to 
collectors
Compare with system 
schematic and reconnect 
properly
Sensors Improper location Compare with system 
schematic and reconnect 
properly
Pump cycles after dark Differential controller Recooling function active 
and max temperature setting 
exceeded
Controller operating properly. 
No fault.
Sensors Defective sensors, sensor 
error
Check wiring continuity. 
Repair or replace
Pump runs continuously Differential controller Off temperature differential set 
too low
Reset off differential according 
to recommendation
Controller set to “on” position Set system operation to 
“Auto”
Pump operated but no uid 
ows from collectors
Air Scoop System air-locked Purge air from air scoop in 
solar pump station by opening 
valve slowly. Caution: after air 
is evacuated uid will ow out 
in a small stream and may be 
hot. Cover port with a rag to 
catch any uid.
Air vent System air-locked Open air vent on the top of the 
system and purge excess air. 
Close after purging.
Fluid Loss of uid from system Locate leak and repair
Isolation valves Valves in closed position Open valves
Piping Clogged or damaged piping Unblock piping or repair 
damaged piping
Pump Broken impeller shaft Replace shaft
Not vented properly Install in correct orientation
Undersized System piping run too long. 
Refer to maximum piping 
lengths and adjust
Noisy system Air vents Air trapped in system Open air vent and purge air 
scoop in solar pump station 
by opening the valve slowly. 
Caution: after air is evacuated 
uid will ow out in a small 
stream and may be hot. 
Cover port with a rag to catch 
any uid.
Pump Bearings are dry or have 
excessive wear
Lubricate or replace
Impeller loose Tighten or replace impeller










