I have a Karcher K5.55m it will not turn off on the machine switch and its making a loud humming sound, pressure is fine and no leaks please can anyone help.

SOURCE: Loud humming noise from subwoofer

if it is a powered sub you should lift the ground. you can do this by adding a three prong to two prong adapter. you know, like when you go to plug something in and the cord your plugging in has three prongs and the outlet your plugging in to only has two. it doesn't have the hole for the ground so you go get a little grey adapter that has three holes on one side and two prongs or tabs on the other.if that doesn't take the hum out (actually, is keeping the hum from getting in) you have a problem with the amplifier.

SOURCE: washing machine will not spin makes loud humming noise

motor coupling needs to be replaced

SOURCE: karcher k7.80 pressure washr

I have a Karcher K 3.86 M electric PW with a similar problem: water leaks from the pump near the outlet and the pressure surges on and off continuously at intervals of 1-2 seconds. The leak appears to be coming from a very thin crack in the plastic pump head in what I think is the "unloader" valve portion. I read elsewhere that if you leave water in these PW's and it freezes it will crack, causing leaks. I don't know how you can empty all the water out so I think we must store these PW's in areas that won't freeze in winter.

SOURCE: Whirlpool top loader won't spin and I replaced the motor and the coupling too

If your basket appears to be off-center in the opening, and there is evidence of the basket rubbing the front of the plastic tub, then you should check out my post at:

http://www.fixya.com/support/t1254687-duet_washer_very_loud_when_spinning

If this is what happened to your washer, the 'burning smell' you refered to was the plastic tub getting hot from the rubbing of the basket (mine smelled the same way, I originally thought there was an electrical failure).

SOURCE: trouble with Karcher Pressure washer

Dear Pgarciax,
It is important that you must have mentioned the model number of your Karcher. Just the same I can surely say that your machine's fault lies in the "SPILL VALVE"
When the gun is open and pressure is being produced, the spill valve is in a relaxed position. Also it has at the bottom a valve, which when pressure is produced it is closed. If this does not close due to dirt or corrosion, the pessure goes down. Now when you close the gun,pressure forces the spill valve down to close the electrical system. Now if the "o" rings of the spill valve are damaged, the machine will start going on and off while in stand-by. So if you know how to locate the Spill Valve, all one has to do is change it with a new one.
In some Karcher machines there are 2 spill valves. One regulates pressure and the other one is for switching off the machine when the gun is closed.
Low pressure could also be due to faulty suction or delivery valves. Most probably the suction valves.
But when saying that there are short interruptions while in stand by, I stick to the fact that the spill valve needs renewing.
Regards,
MG.