Washing machine drain pump

[D.M. Procida]

The drain pump on our washing machine buzzes quietly, but doesn't spin the impeller.

It's a Plaset model 57605, and looks pretty much like the one illustrated in bits at

under the heading "Magnetic or Synchronous Pumps".

I can't see anything wrong with it - there doesn't seem to be anything to go wrong! I've had it apart, cleaned it up and so on. There was water inside, but I don't think that matters with this kind of motor.

The rotor moves freely enough, flicking nicely btween its poles.

Anything else I should check before buying a new pump?

Thanks,

Daniele

[D.M. Procida]

It's difficult to tell with the resistance of the magnets.

Should the rotor be quite dry behind its seals?

However, before I took it apart, I could get it to start oscillating with the flick of a finger. However, it would only oscillate weakly, not spin properly.

I have noticed that while there is a little hum from the motor, the buzzing actually comes from elsewhere in the machine, though that stops if I disconnect the motor.

Daniele

[mick]

I've just had a similar problem with one of these (on a Beko washing machine). The outlet hose was blocked!

[fred]

In article , D.M. Procida writes

Check that turning the impeller by finger actually turns the motor, it's not uncommon for the impeller to lose grip on the shaft.

When mine went I found that a replacement was overpriced so dismantled it and found that that the impeller screwed onto the motor shaft and that the shaft thread had corroded and lost grip on the moulded in nut.

In a nothing to lose move, I unscrewed the impeller, repeatedly immersed it in boiling water to wash away soap residues, degreased with alcohol, then filled the hole with epoxy, smeared some on shaft, re-assembled, poured in more epoxy and used a hot air gun to get it flowing into all the gaps.

I used a plastic shim between the impeller and the pump body to keep the impeller oriented while the epoxy set.

Six month later and it's still holding.

[Tabby]

Connect pump direct to mains to check its getting power properly. If it is dead, just take one off a scrap machine, generally it doesnt need to be the same make or design, just check the diameter of the inlet.

NT

[D.M. Procida]

The impeller has a distinct 180-degree free rotation on the shaft, with hard stops at either end. I presumed this was part of its design.

Daniele

[fred]

No, it should spin freely (but be connected rigidly to the motor), summut is up.

Dismantle and have a play, you have nothing to lose.

[D.M. Procida]

As I said, I have dismantled it.

I haven't tried removing the impeller from the shaft, though. The way the impeller moves on the shaft, with 180 degrees of freedom between its stops, suggests that it's part of its design (and related to the poles of the magnets and the way the motor works).

Daniele

[fred]

In article , D.M. Procida writes

Knowing the way an impeller pump works, that seems unlikely.

[D.M. Procida]

I assume that it's something to do with the way the poles align depending upon which way the motor is spinning, to give the motor a maximum arc of free movement to get started, even if there is water in the pump.

Daniele

[Fredxx]

If you're feeling "magnets" then it either isn't a single (shaded) pole induction motor, which is what I would expect to see, or its an induction motor with wrecked bearings.

How may wires go to the motor? If only 2, then you're probably feeling the bearings which have "high" spots.

[Skipweasel]

The pump on both our current and previous washing machines had "magnetty" stiff points twice per revolution. They worked fine.

[D.M. Procida]

Thanks for all the advice.

I thoroughly dried the rotor and the plastic body it fits in to, and added some grease.

The key to success seemed to be getting the rubber O-ring in the right place. It's not obvious where it should sit, but once it was in the right place the collar of the pump fitted most closely.

Anyway, the machine now runs and drains again, so the threat of having to get a new machine has once again been postponed.

Daniele

[D.M. Procida]

It's definitely magnets, not high spots in the bearings or any kind of mechanical resistance.

It's not an induction motor, but a synchronous motor.

I think that's why it has the 180-degree free movement of the impeller on the shaft - that allows the rotor to begin rotating freely, without the resistance of the water against the impeller.

It has to hit 50 revolutions/second from a standing start in order to synchronise with the mains, and it would stall if it had to do that against resistance.

Daniele

[Skipweasel]

The other reason they use 180=B0 motors is that it makes them more likely= =20 to be self-clearing. If they always went the same way round as a 120=B0=20 motor would, for example, crud could get stuck in a hole. Having the=20 rotor come round and smack the bit of Lego from the other side helps=20 chuck it out rather than wedge it tighter.

--=20 Skipweasel - never knowingly understood.

[D.M. Procida]

That must be where all the small Lego pieces have gone in this house! Instead of safely blocking up the washing machine so they can be retrieved, they've just disappeared down the drain.

Daniele

[Skipweasel]

It must go somewhere - they've been making the stuff for over half a century. By now the entire surface of the earth should be around 1/2" deep in it.

If you want more small bits -

[D.M. Procida]

It looked exactly like the one in the link above!

Again:

Daniele