Tip & How-To about Miscellaneous
Karcher K4 pressure washer.
Unit was dead; no action from pump when switched on. Previously it was intermittent.
Cause of problem: When the unit is switched on the pump runs until the pressure head is pressured up. At this time a small spring loaded pin is forced into the switch assembly, and pushes on a lever which operates the main rocker switch, and the pump turns off.when the lance trigger is pressed on, the pressure in the head drops and the pin withdraws allowing the pump to run. As a result of age or much use the pin may become 'sticky' and thus reluctant to return. My unit had the pin stuck fast. I could not see an easy way to get at the pin to clean it, so I worked it back and forth using WD40 and then grease until it moved freely. The pressure head in my unit is alloy and the pin is stainless, an unhappy combination of metals. I believe later units have a plastic pressure head and I can foresee similar problems occurring as the plastic ages. It is probably good practice to always make sure the pressure is relieved before storing the unit after use so that the pin defaults to the withdrawn position.
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