KARCHER pressure washer - motor fault

pen4uk · 1 Jul 2020

Hiya you knowledgeable people,
OK, I have a KARCHER 390 old model. its been fantastic up until now. First issue was, it suddenly stopped working done some digging and found it had a leak on one of the cylinder head seals ok replaced that stopped the leak. All good I thought but no. With the cover off water on full, and hold the trigger fully open and push the fan on the back of the motor it springs into life BUT as soon as I let go of the trigger it will not start again until I push the fan and then its fine until I release the trigger then back to square one again. is it the Brushes? if yes how do I do that ?

Burnerman · 1 Jul 2020

Check out the motor capacitor first, look for burning or any discolouration.
These components instruct the motor in which way to spin, and if its faulty this is the symptom you get.
John

jj4091 · 1 Jul 2020

I agree with John but I doubt there will be any physical signs of damage & testing them yourself is difficult. If you can still get them & for what they will cost I would just replace it as a first step.
https://www.buyspares.co.uk/pressur...753&shop=karcher&path=68311&model_ref=8498042 or much cheaper one https://www.ebay.co.uk/i/2914544947...MI_8O55q-s6gIVj-vtCh1ePwoiEAQYBCABEgIyCPD_BwE

pen4uk · 1 Jul 2020

Burnerman said:
Check out the motor capacitor first, look for burning or any discolouration.
These components instruct the motor in which way to spin, and if its faulty this is the symptom you get.
John

Hiya John, I think you've hit the nail on the head.
When I prod the fan it spins to the left and when I do it again it spins to the right.
Where is the Capacitor located? Would it be in the little black plastic box on top of the unit.
Thanks for your help
regards Colin

Burnerman · 1 Jul 2020

A motor capacitor is generally a shiny aluminium cylinder (closed ends!) often bolted to the motor itself or certainly nearby. It will be marked with its working voltage and capacitance measured in microfarads or uf.
Typical voltage could be 400v and capacitance 4uf.
We’d need a photo for more recognition I think.
John

pen4uk · 1 Jul 2020

Thanks for that I will have a look in the morning when I get home from work.
many thanks

SFK · 1 Jul 2020

Try this... images of capacitor used in karcher, and instructions on how to replace.
https://www.google.com/search?client=firefox-b-d&q=KARCHER+390+capacitor

Strange as there seem to be many different recommendations for this capacitor - between 20uF and 50uF.
You might have to open the katcher first to see the capacitor rating.
SFK

pen4uk · 1 Jul 2020

Burnerman said:
A motor capacitor is generally a shiny aluminium cylinder (closed ends!) often bolted to the motor itself or certainly nearby. It will be marked with its working voltage and capacitance measured in microfarads or uf.
Typical voltage could be 400v and capacitance 4uf.
We’d need a photo for more recognition I think.
John

I couldn't wait until the morning John

Burnerman · 1 Jul 2020

SFK said:
Try this... images of capacitor used in karcher, and instructions on how to replace.
https://www.google.com/search?client=firefox-b-d&q=KARCHER+390+capacitor

Strange as there seem to be many different recommendations for this capacitor - between 25uF and 50uF.
You might have to open the katcher first to see the capacitor rating.
SFK

That’s pretty high for a motor start cap.....oh well! Plastic or metal, the markings are the same.
John

pen4uk · 1 Jul 2020

Hi John,
I've located it,
on my unit it has this,
Icar Italy Ecofill
WB 40200
20 UF
AC 400V
And the closest I've found is,
Icar Italy Ecofill
WB40400
40UF
AC 400
is this any good?

Burnerman · 1 Jul 2020

Hmmm certainly the working voltage is fine but the capacitance -40 against 20uf.
I’m afraid I’m not able to comment if that is ok or not and no idea what difference it would make but I’d prefer to get one nearer the original rating.
John

SFK · 2 Jul 2020

Not important> Icar Italy Ecofill
Not important> WB 40200
Most important> 20uF (must be at this value)
Make sure at or above> AC 400V (no issues with this being AC450V or AC500V).

You will want one of these:
ebay search "Karcher 20uF"
https://www.ebay.co.uk/sch/i.html?_...0&LH_TitleDesc=0&_osacat=0&_odkw=katcher+20uf

Or these:
Google search "Karcher 20uF"
https://www.google.com/search?client=firefox-b-d&q=Karcher+20uF

Or if you have the money this is likely to be closest to OEM:
https://www.espares.co.uk/reviews/es538532

SFK

Burnerman · 2 Jul 2020

Anyone have any ideas what happens if the wrong value capacitor is used?
John

SFK · 2 Jul 2020

If the wrong capacitor rating or a poor quality capacitor is used, then the motor will not have the correct phase angle between the current and the voltage, and consequently the motor torque or rotational force will be affected. Depending on the motor load, this may result in a reduction in the motor's overall speed.
No idea what the tolerance is. Would need to know inductance of motor i presume.

jj4091 · 2 Jul 2020

Burnerman said:
Anyone have any ideas what happens if the wrong value capacitor is used?
John

In the old days if it was a long way out of tolerance the motor would lock up & begin to smoke, probably because of SFK's description

diynot

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

KARCHER pressure washer - motor fault

Similar threads