Earth leakage problem on Kärcher pressure washer

Hi all. Talented amateur here, stage electrician at school 1971 - 74 and have done much DIY electrical work iover the years, including central heating systems. I worked for several years for the residential division of Honeywell Control Systems and wrote many installation and user instructions for heating controls.

I have a Kärcher 520M pressure washer which has given excellent service over the years, but using it to jet a drain problem a few days ago and it stopped working and my wife noticed that much of the power in the house had gone off. The washer has a powerful induction motor.

Our consumer unit is a split system with two RCDs, and the house supply is PME, one of which was off. It reset ok but once the pressure washer was turned on again, off the RCD went. The 13A fuse in the washer's plug did not blow.

A bit of online searching suggested the pump motor's starter capacitor was the likely culprit, a 25ùf device, so I ordered a new one and it came the next day. First time I tried it, the pump twitched into life, but then the power went off again.

It has been suggested that a small water leak between pump and motor could be responsible, but I have been unable to strip the washer down far enough mechanically to investigate, but will persevere. The electrics are pretty well isolated in the control box and there's no obvious way water could have got in and caused an earth leak. I wonder whether the in rush current from the starter capacitor could have triggered an earth leak, but I am reluctant to junk an otherwise serviceable capacitor.

Comments, suggestions much appreciated.

Thanks very much.

 

Thanks Bluejets.

Understood about possible water ingress. I will investigate. I do not own a megger, I'm afraid, just a good multimeter.

 

Thanks Bluejets. Looks like I need to found a proper sparks then.

 

Will do. Just bought a Metrel multifunction tester so will see how that gets on.

 

Right. Couldn't afford any Megger. Bought the metrel cheap on Ebay. It should be here in a couple of days.

 

Any idea what I should be testing woth the Metrel when it arrives?

 

Will do, as soon as it arrives.

The original trip was on the house RCD, not a fuse or MCB. This happened first when I was jetting a drain run and the machine just cut out. It was plugged into a four-way extension lead and then into a wall socket. Did a bit of searching and it was suggested the starter capacitor 25uf, could be at fault. I ordered another one and tried the replacement. The machine pulsed on for a second and then cut out, with the RCD having tripped again. Further reaerch suggesting possible water ingress past a seal between pump and motor. Now I need to strip the whole thing down and investigate. Replacement cap showing 24.6uf and the original 23.19.

 

Hi Bluejets. I expect you're thoroughly bored with my problem now.

I have read everything you have written on this thread, but no need to worry about deja vu.

Yesterday I began stripping the washer down. I had had to get some impact torx bits as I had been unable to free the bolts that hold the pump and cylinder head together. As everything came apart a grey liquid started to drip out and onto the floor. I couldn't tell if it was water, or oil or a mixture of the two. There was a quantity in the space where the swash plate and bearing are located, between the pump and the motor. It's a brushless motor. I managed to get the spill valve out eventually, with some difficulty and also the inlet strainer; new ones required I feel.

I think I am still some way from being ready to reassemble and test. I don't know if the washer is supposed to contain oil and if so, what grade and where it goes. I have emailed Kärcher UK's helpline to see if they have any ideas.

Maybe it's time to buy a new pressure washer. Mine has given excellent service over the years and I hate to throw away things that can be mended, but manufacturers don't always help.

 

Hi Bluejets and thanks for your continued interest - much appreciated.

I took the whole motor out of the casing yesterday. As there had been a lot of liquid (grey, oily watery stuff) coming out of it the previous day, I didn't think there was any point doing any electrical testing until I had ascertained whether the motor could be salvaged mechanically. Control box and wires disconnected and fed back throught the aperture in the motor case.

Lots of water visible and I mopped up as I went, blowing the casing clear with the air line. CLamped the motor casing in an engineering vice and tried to undo the bolt on the rotor shaft so I could get the fan off. With a Torx 30 impact bit (set bought earlier in the week) and my compressed air impact driver. The fan just fell off!

Spent quite some time cleaning up the motor shaft, which was rusty and a bit wet, drifting out bearings, cleaning them up and regreasing them, then lots more blowing out with the air line.

Reassembled then left overnight - even the swash plate is back in place. Tightened up cheese headed bolt this morning and remade electrical connections. Resulto - motor started on the new capacitor and hummed away merrily. Looks like the wires that connect to the microswitch are wired in directly to the field coils in the motor windings inside the casing. No sign of water on them; looks like I did a fair job of drying them off yesterday. I left the earth wire reattached to the mounting point in the casing pending testing.

NOw to figure out what the pump assembly needs - oil - seals, gaskets, spill valve etc.

What tests should I do on the wires to the motor btw, since everything else seems to be ok, electrically?

Many thanks, Bluejets. WIll carry on looking for a service manual for the machine as suggested.