Separate electrical symptoms from hydraulic symptoms. A silent pump with no indicators is different from a motor that hums, a pump that runs without moving water, or a system with weak flow.
Symptom table
| Symptom | Likely checks |
|---|---|
| No sound | Controller state, interlock, timer, outlet protection, documented reset. |
| Hums but does not turn | Blockage, seized impeller/motor, low voltage, capacitor or motor fault—disconnect and escalate. |
| Runs but no flow | Prime, air lock, closed valve, suction leak, blockage, incorrect direction. |
| Weak flow | Dirty filter/strainer, hose restriction, worn impeller, system head. |
| Runs hot or cycles | Dry running, blocked ventilation, overload, restriction, supply issue. |
| Leaks | Housing, union, O-ring, seal, freeze damage, pressure problem. |
Checks that do not require opening the pump
- Confirm water level and valve position.
- Inspect the plug, cable, and dry connection area without touching damaged equipment.
- Check the filter and strainer.
- Prime and vent only as documented.
- Observe whether the controller is requesting pump operation.
- Compare sound, vibration, and return flow with normal.
Do not bypass protection
Flow switches, GFCI/RCD devices, thermal protection, and controller interlocks exist for a reason. A repeated trip is a fault signal, not an inconvenience to defeat.
Related guides and tools
- Chiller troubleshooting hub
- No-water-flow diagnostic
- Pump troubleshooting
- Chiller size calculator
- Water-volume calculator
Power-side checks
Keep hands and connections dry. Confirm the controller is calling for pump operation, the documented interlocks are satisfied, and the protected outlet has not tripped. If GFCI/RCD or breaker protection trips again after the permitted reset, leave the equipment off. Do not use an extension, adapter, or unprotected outlet to “test” it.
Hydraulic-side checks
A powered pump cannot move water when its intake is blocked, housing is full of air, a valve is shut, a hose has collapsed, or the filter is excessively restrictive. Confirm water level, prime, suction path, strainer, and discharge before assuming an electrical failure.
Humming pump
A hum without rotation may indicate a jammed impeller, seized motor, failed starting component, low supply voltage, or internal damage. Disconnect power. If the manual permits owner access to the wet-end cover, inspect for debris with the correct procedure. Do not open sealed electrical sections.
Noisy or vibrating pump
New noise can follow cavitation, air, debris, damaged impeller parts, poor mounting, or bearing/motor wear. Danner lists debris in the volute and damaged impeller support components among causes of noise and vibration. Stop repeated operation if the sound is harsh, the housing heats quickly, or flow falls.
Pump runs hot
Dry running, low flow, blocked ventilation, excessive restriction, overload, or internal faults can raise temperature. Do not cool an electrical motor by spraying it. Shut down, allow safe cooling, and correct the cause.
Leak classification
- Union/O-ring: inspect seating, damage, cleanliness, and approved lubrication.
- Housing crack: replace the affected component; do not rely on improvised patching under pressure.
- Shaft or internal seal: obtain model-specific service.
- Condensation: verify the source rather than assuming every puddle is a plumbing leak.
Replacement decision
Match flow at system head, continuous-duty rating, fresh/salt-water compatibility, temperature range, plumbing size, electrical listing, and installation orientation. Danner’s product pages show that pumps with similar maximum GPH can have different duty and application limits.
Reference
Danner pump troubleshooting FAQ and the manual for the exact installed model.
Restart after debris removal
Reassemble every wet-end part in its original direction, confirm seals are seated, restore water and prime, then watch the first startup from a safe dry position. Verify strong flow, normal sound, no rubbing, no leak, and no rapid heating. Stop immediately if the pump stalls again; a damaged impeller, shaft, bearing, or motor may need replacement.
Information for a replacement pump
Record the current model, voltage, watts, continuous-duty status, plumbing diameter, vertical rise, total loop, filter, chiller flow range, installation orientation, and whether the pump is submerged or inline. Choosing only by maximum GPH can create excessive pressure, noise, poor filtration, or inadequate real flow.
Can the pump be tested outside the loop?
Only use a manufacturer-approved bench or bucket test with correct submersion, priming, voltage, grounding, and outlet protection. Never energize a pump dry or handle a powered pump in water. A qualified technician is safer when the fault may be electrical.
Why does a new pump still have weak flow?
The installed loop may have more resistance than expected, the plumbing may be reversed, the filter may be restrictive, or the pump may not suit the required head. Verify operating conditions instead of assuming the new unit is defective.
Record the final repair and verified operating flow for future comparison.
