The Kärcher HDS 10/20 is a high-output commercial hot-water pressure washer intended for sustained work. Depending on its exact production version, the model combines roughly 200 bar capability with about 1,000 litres per hour of water flow. Its three-phase supply, larger pump and diesel-fired boiler make correct diagnosis especially important.
Confirm the exact HDS 10/20 version
Start with the full model, part number, serial number and data-plate photograph. HDS 10/20 variants and production revisions can differ in their controls, sensors, ignition equipment and service parts. The supply voltage and plug arrangement must also be recorded before testing.
Three-phase electrical faults
A missing phase, incorrect phase rotation, poor plug connection, damaged contactor or weak site supply can cause starting problems, protection operation or incorrect motor behaviour. Electrical checks must be completed by a competent person using equipment suitable for the supply. Repeatedly resetting a tripping machine risks further damage.
Pressure and water-flow problems
- Restricted inlet supply or contaminated fine filter.
- Incorrect or worn nozzle affecting pressure and motor load.
- Worn pump seals, pistons or inlet and delivery valves.
- Unloader, control-piston or pressure-switch faults.
- Leaks at the pump, hose reel, trigger or boiler pipework.
Pressure and measured water flow should be considered together. A smaller nozzle can produce a sharp jet while hiding reduced output and placing unnecessary load on the pump and motor.
Burner faults on an HDS 10/20
A machine that makes pressure but not heat may be missing a flow or temperature-control input, or have a fault in its fuel, ignition, airflow or flame-monitoring system. Smoke colour, fan operation and behaviour after trigger cycling provide valuable clues. Persistent smoke, pooled fuel or an exhaust-temperature warning means stop.
Scale protection and heating performance
Correct system-care use and water-hardness setup help protect the heating coil. Scale can reduce heat transfer, restrict flow and increase stress on the boiler system. Poor heating should be diagnosed before chemical treatment or parts are chosen; burner and control faults can create similar symptoms.
What a proper service should prove
- Correct electrical supply and safe motor operation.
- Stable pressure and expected flow under working load.
- Sound pump oil and no water or fuel leakage.
- Clean burner ignition and controlled heat-up.
- Safe shut-off and reliable restart after trigger cycling.
- Operation of warning indications and safety controls.
See our dedicated HDS 10/20 repair service →
Send the model and symptoms, or ask us to help match a machine to the work.