Karcher pressure washer broken again?

[thermidorthelobster]

I had a little Karcher pressure washer which broke after light use;  the switch that switched it on and off with water pressure failed, and so much of the rest of it was also knackered that I had to throw it away.

So I bought a bigger one, a Karcher K650M which has a drum design which seemed to be slightly more robust than their conventional ones.

The last couple of times I've used it, when I use the wand on full pressure, the motor cuts in and out - about 2 seconds on and half a second off.  If I use the pressure setting on the wand to lower the pressure, then it works fine, but of course it's useless for cleaning because the pressure's too low.  If I use a brush it also works fine.

I thought maybe the supply pressure was too low to maintain the flow of water, so the motor was cutting out to avoid cavitation, but the mains pressure here is eyeball-removing, so I can't see that's the case.  Additionally, the machine's designed to suck water out of a water butt if necessary, so it shouldn't need positive pressure at all.  It has an inlet filter but this is perfectly clear.

Any suggestions from somebody who knows their way around a Karcher pressure washer, or are they just basically a pile of cheap rubbish that doesn't last five minutes?

[waveydavey]

That sounds like the bit on the wand is basically a flow restricter; like a gun on a  hosepie in effect.

If you have high flow (lower pressure) then the pump keeps going to try and get pressure.

If you slow the flow (higher pressure) then the backpressure gets to the cut out pressure and it stops the pump to avoid damage.

It really should be set though so it runs continuously even at maximum pressure; the pressure switch in it may be set a bit light?

[Bishops Finger]

Mine normally does this thought it was the flow of water from the tap because if the tap flow is too grate hose couplings come undone

[waveydavey]

It could actually be that the pump and mains pressure combined are causing excess pressure; try throttling the tap a Little bit; obviously not so much that it may go dry but they really don't use a lot of water.

[piggysteve]

Sounds like lack of water, in our big Karcher at work there's an in line filter where the hose connects to the machine.

Steve

[paul_humphreys]

Do as I did, take it apart and "fix" it so the pressure is on all the time. Its easy to when its apart.

Paul

[mike142sl]

Do as I did, take it apart and "fix" it so the pressure is on all the time. Its easy to when its apart.

Paul

I have the 620M version - an older model but with a similar prob. Took it apart but no sign of any pressure switch. What does it look like?

[andyw]

I had a similar problem on a Kew washer, and the problem was a small bit of grit in the end of the lance nozzle, so when on full power it was building up too much pressure.

[thermidorthelobster]

Thanks everybody;  I'll try backflushing the lance and turning the tap down, and if that doesn't work I'll pull it apart and glare at the innards for a while.

[Manicminer]

Run a hose from the tap into a large bucket and then let the pressure washer suck the water out of the bucket. That was the advice given about 20 years ago when pressure washers were sold to the public in the early days.

[V8MoneyPit]

I've owned that model for a few years and it's performed without fault. I use it on a very long hose and it's never given trouble.

[jiffyman]

I wont touch Karchers, had no end of problems, all with the pressure switches failing!!!!!

It did the cut in and out thing on all of them.

Spoke to a bloke at the place i bought them and he said it was a common 'little known' fault with them!

Eventually went for a cheap B&Q own brand, had it 5years now, never let me down at all

[waveydavey]

Run a hose from the tap into a large bucket and then let the pressure washer suck the water out of the bucket. That was the advice given about 20 years ago when pressure washers were sold to the public in the early days.

That is akin to throttling the tap a bit but even better.

Think of it another way; if your mains water pressure was high enough then the pump would never need to run and it would be fine. All you really have is half way there, the mains water is doing half the job of the pump so the pump only works half the time.

[paul_humphreys]

Do as I did, take it apart and "fix" it so the pressure is on all the time. Its easy to when its apart.

Paul

I have the 620M version - an older model but with a similar prob. Took it apart but no sign of any pressure switch. What does it look like?

If you take it apart. You will see the main part, its hard to explain. You will see the peice that works the pressure on the motor. It can be ajusted, but I fixed it so its at full pressure all the time.

If I can find a parts list, I will post it.

Paul

[mm77]

Run a hose from the tap into a large bucket and then let the pressure washer suck the water out of the bucket. That was the advice given about 20 years ago when pressure washers were sold to the public in the early days.

On mine I always keep the handle on, power off and turn on the tap, so water mains pressure runs though, then turn off the handle. Then power on,  This one does not get air blocks in the system which causes pumps to fail.

[thermidorthelobster]

I had a good look around the internet and everything points to it being the spill valve.

So I finally got around to dismantling the damn thing and cleared and greased the spill valve.

No joy.  Exactly the same as before.  Suffice to say this is the last time I'll be buying a Karcher pressure washer, given it's the second one I've bought that's had light use, been looked after and then the spill valve has failed rendering the machine useless.  Stupid piece of...

[davidlandy]

got a nice big diesel drive karcher - turn the pressure and temperature and it removes your paint!
 :oops:

[Big Watty]

Do you have the hoselock connection on your hose that stops the water coming out when there is nothing connected?

If so try taking it off and have a "normal" connection - I had the same problem as you and changing the connector solved it

[mike142sl]

Do you have the hoselock connection on your hose that stops the water coming out when there is nothing connected?

If so try taking it off and have a "normal" connection - I had the same problem as you and changing the connector solved it

Now that IS a helpful comment - I think mine started to be problematic at about the time I fitted one of those hose lock fittings. I shall try taking it off and see what happens.

[thermidorthelobster]

Do you have the hoselock connection on your hose that stops the water coming out when there is nothing connected?

If so try taking it off and have a "normal" connection - I had the same problem as you and changing the connector solved it

Thanks for suggestion - unfortunately it doesn't seem to have solved it for my heap of junk but cheers anyway!  Next time I'll try a whole different hose from the tap just in case.

[littlepow]

got a nice big diesel drive karcher - turn the pressure and temperature and it removes your paint!
 :oops:

Used to fix and service industrial steam/pressure cleaners and got sent to a farm when a farmer complained his old grey tractor had turned silver when he washed it. Then promply went to prove the point on his shiney new red tractor, which when he had finished had a nice shiney silver patch due to lack of paint! Had to show him that the steam setting wasn't the best choice for removing mud and he may just want to use the cold setting in the future.