my karcher 411a preasure washer has lost 50%of waterpressure when switched on motor seems okchecked water inlet can you helpjdwootton

jdwootton, June 2009

I've been told the motor on my 411a is u/s but it was working before I put it away for winter? The motor does appear to be seized as it doesnt start but blows the mains fuse. I think it's jammed and must be able to be stripped/cleaned?

John, March 2017

It will probably be the pressure relief valve you will need to open the case about 9 torx screws and remove a d circlip on the pressure valve assembly. Have a look at the exploded pasts page from the Karcher site.
The valve needs to be turned about 90 degrees to remove but probably both ears have broken and it will fall out. A new one will cost around £29.00 pound from a spare place.

1caloun, July 2014

Couple of years ago I didn't drain my K411A pre-winter and it (I think) cracked a gasket. Still worked ok but pees like an incontinent dog. But now!!...
the on/off switch doesn't work... the motor starts as soon as the power is connected. My wife says 'dump it and get another' but I'm a sentimental soul. (She would have already gone by that route if I wasn't!) Any ideas, guys?!

boldward, July 2013

refitted a cylinder head, the washer wont cut out when the trigger is off. have i fitted all correct

andy, April 2013

my 411a runs for about 4 mins then cuts out for 2 to 3 mins then start again this keeps happening over and over again

norman hodgson, August 2010

I have been using my Karcher 411A for a while. It's afew years old but has worked fine. Last time I used it the pressure suddenly failed and the motor seamed to buzz. after turning it off for a while it worked again but soon stoped again with the same buzzing sound. Any suggestions

jon loveday, May 2010

Note : karcher made 2 versions of the K411 and one had the modern plastic pump but the older machine 19949720 had the aluminium pump..... if you have the older ally pump model you will see 3 white plastic recessed valve cover on top.... the older machine will loose 50% pressure if the dump valve breaks (this is the common fault after several years use). The dump valve is code 9001135 and available from www.sparesgiant.com for about £20.
LOOK ON THE SILVER DATA STICKER and check the first 8 digits of the barcode. the older version is 19949720

john, September 2009

Hi jd,
I've fixed mine by stripping and cleaning the pump head.

First get a TORX screwdriver, T 15, with a long enough shaft and part the 2 halves of the machine.
You will need to identify the pump head.
Have a metric allen key as well to take the pump head off.

Get yourself a diagram from espares.co.uk website.
Select "pressure washers"
Go to K3 series machines.
Find K301B TV. (Same pump)
Look on the left side for a panel that gives "parts diagrams".
Select "cylinder head".
See exploded view, copy/print it for future(if this is your model) there are early and late versions of the 411a.
If not open up other 3 series machines because your pump will undoubtedly be on another model.
See items 10,15,16,17,18.
This is where the debris was on mine, particularly 17, holding the valve open, hence no pressure.
Mine functions now but doesn't seem powerful enough and I suspect valves 15 and 10 have worn faces allowing some loss of pressure(back flow)
The 15 set is a couple of quid elsewhere on espares I'm not sure about the others but the web will track them down.
First off, strip and clean. Most items come apart with a firm pull but be careful to get the deterg lever(4) correctly hooked under the pump/on/off lever when refitting the head because it works the on/off switch as well.
Take care to ensure all o rings /seals etc are correctly positioned on assembly as they are easily damaged.
Lastly, fit the piston seals, if good, to the pump body first. Ensuring they are the right way round, sealing lips inward. Lube with washing up liquid when fitting head back to pistons.
Piston seals are in packs of 3 from spares people, as are all the little valves.
Clean up first and this may be all you need.
Don't use dirty water for the machine, tap water only!!
Most problems are from using water from drums/tanks etc
If all else fails, call Karcher on 01295 752000
Regards

t.r.services, July 2009

jd,
i've just retrieved one of these from my local recycling centre bin. It runs etc but pressure is low. On the other karcher i have the same fault turned out to be a small nylon valve assy that triggered the high pressure circuit. cost a couple of quid, fixed in a jiffy. That little sucker fell out when the high pressure hose was removed so watch out.
If I get my 411a sorted I'll tell you how and how much. Cost of new machines will limit fix to £10 though.
Get an explode view downloaded and see if any of your little valves are damaged/split o ring etc

t.r.services, July 2009