pressure washer fault finding

[Norm]

Hi Guys, anyone up on pressure washers? used mine today for some serious patio / driveway cleaning before the winter sets in, it ran fine for about an hour then stopped with a loud buzzing sound coming from the motor and no pressure from the Lance, I left it for ten minutes or so and it started again but made the same buzzing sound then stopped. Figuring It was dead and with nothing to lose I stripped it down expecting to find the head of the pump cracked or the valves or pistons or whatever there called damaged, but everything seems fine, nothing broken and all turning and moving as they should, the head seems fine with no cracks evident the only problem I could find was the electric motor itself, the casing was seriously hot even an hour after it stopped, yet it spins freely, the fan is attached and it ran when i switched it on without the pump part attached. I plan to re assemble it tomorrow if I can remember where all the bits go and see what happens, any ideas why it would overheat It's a cheap machine but has given good service and has ran longer than an hour previously with no issues. Thanks in advance Norm

 

[stormin]

I would instantly suspect the motor start capacitor if there's one fitted. It'll be on it's last legs if not completely failed and not just kicking the motor round. That's why it's sat there humming and not spinning. The capacitor introduces an artificial second phase into the windings to help turn the motor.

 

[Norm]

Cheers stormin, sorry I'm bit lackin in knowledge on electric motors, I presume the capacitor is the long cylinder attached to the motor casing, is there any way I can test it or is it replace and see if it works.
Regards Norm

 

[stormin]

Yes that'll be the item. If you've got a fancy multimeter you can test for capacitance should be a reading on the side of the cylinder somewhere along the lines of 25uF, that's micro farads.

If you've only got an ordinary multimeter you can test using the resistance ohms feature. First short the two wires or terminals of the capacitor to discharge it. Then attach the two leads from your multimeter. You should see the resistance slowly climbing to a peak value. Even if it does this it's no gaurantee that it isn't slightly low on capacitance anyway and another small capacitor in parallel may help provide enough shove.

If there's any doubt it may well be worth a tenner to replace the capacitor.
IF there's a fan on the motor sometimes just a quick flick of this will get the motor turning and running which will help eliminate any other potential causes.

 

[Norm]

Cheers Stormin there are some numbers on that part which I spotted when takin it to bits I shall see if I can find a replacement where's best to get one Ebay or maplins spring to mind?

 

[pedrobedro]

I bought one for my skip find pressure washer. £7.50 from a local electronics shop and it works fine now. I had a clue though, the old capacitor had melted

 

[Norm]

I had a clue though, the old capacitor had melted

bet that helped in narrowing down the fault then

 

[eil]

You don't have or even know someone with a clamp on ammeter you could borrow, as there is a pretty good test for capacitance you could carry out first.

 

[Norm]

Hi Eil I do have a very good mate with such an item whats the test please

 

[eil]

You need to set your meter to volts a range around 600v and then connect the leads across the capacitor terminals to measure the voltage the motor is generating, also connect the clamp meter around the wire from the capacitor to the start winding to see what amperage its drawing, when you have the voltage reading and the amp draw reading use this formula to give you the capacitance,
Amps x 3180 divided by the voltage.
this is how I tested my compressor capacitor under load I have a meter that shows both volts and amps at the same time if your meter doesn't have this facility you just flick the dial between the two to get your readings. A few pics to try and help explain what I mean.
As you can see mine is showing 5.06 A and 386.6 V
5.06 x 3180 = 160908 then divide by 386.6 which gives us 41.6 microfarads.

 

[Norm]

Thanks eil I shall give that a go before buying anything,
Last question guys what oil do I put back in the pump ? the old stuff was milky white and has never been changed in the eight years I have owned the machine, to be honest I didn't even know there was oil in there. A google search suggests 30w non detergent oil which seems a pretty rare beast however some other sites suggest either gear oil or transmission fluid so I'm totally confused as to what to use

 

[penfold]

Compressor oil is probably a good bet; the common grades are usually 20 or 30 grade.

 

[KemppiFrog]

The local agri place stocks 30 grade (and other) oils for garden equipement.
You might try one in your area.
KF