Hi, I’m a moderator for this topic and I wonder whether you’re still waiting for an answer. If you are, please let me know and I will do my best to find a Professional to assist you right away. If not, feel free to let me know and I will cancel this question for you. Thank you!
Press CTR D for www.justanswer.com/home-improvement/expert-dr-fix-it
When the gun is closed, there is a spill valve that contracts with the built up pressure and at the same time works on a micro switch which cuts the electric power, thus stopping the electric motor. Now in many cases when the gun is again opened, this spill valve sticks and keeps the electric circuit from closing. In all cases you must open the cover, and locate this spill valve. Sometimes it is easy to see a micro switch on it. If you remove the micro switch from the spill valve the motor will for sure turn back on. the spill valve gets stuck for many reasons. One of the reasons is that you leave the machine under pressure for a long time and even stored away the machine with pressure still in the system. A spill valve also gets stuck due to detergent. You can try service the spill valve and lubricate with special silicon grease. Otherwise, can change the spill valve with a new one. So in a few words, the spill valve is stuck and leaving the microswitch off. So the electric motor cannot turn. Also, sometimes the spill valve is difficult to remove. You can try to attach water supply and switch on the pump. With the pressure produced the spill valve may slowly be pushed out.
reference - http://pressure-power-washer.com/karcher-manuals.htm