White Knight tumble dryer - drum not turning

If it uses an electrolytic capacitor that would explain why the capacitor fails. Most of the dryers I've dealt with have oil filled run capacitors, as does my drill press and the fan motors in my furnace and heat pump, those are are all the PSC motors I have I can think of other than the refrigerator compressor, dunno what sort of cap is in that, I've never looked.

refrigerator compressors dont have a capacitor.

Sure they do, they (again at least in the US) have a PSC motor in the compressor, usually the capacitor is 8-15 uF potted brick but I've seen older ones with oil filled capacitors.

Not in the UK they are relay or PTC starters no capacitor

In UK, older ones used to have a start capacitor and relay (starter relay failing was a not uncommon failure mode in old age).

There's no externally visible capacitor in current models, but they are certainly induction motors of some type.

Must be damn old I been working on them for 25yrs never seen one with a capacitor only a relay starter

They are usually two identical windings with a capacitor between them. The control box feeds each side of the capacitor in turn for a few seconds. This gives a few seconds of rotation in each direction. If the capacitor (or a winding) is open circuit, it won't start without assistance.

That looks like the most significant paragraph in your original fault description.

It doesn't run until you poke it... which suggests that there is only a single phase connected, which could be power only to the Main winding or only to the Auxiliary winding (the one via the capacitor).

But even when poked it has no torque.... which then suggests that only the Aux winding is being powered.

It looks like it could be a poor connection to the main winding of the motor, or the main winding itself.

It's an ohmeter job. Locate and check continuity of the main winding, then work backwards along all wires and connections to it.

Perps, in order of probability:-

Any switches, switching or reversing power to the main winding. The main winding itself. Crimps and connections along the wiring.

If no obvious fault is found, do the same ohmeter exercise in the Auxiliary path, (just in case), particularly checking the capacitor for short circuit along the way.

There is often a thermal cutout embedded in the winding. The often fail after repeatedly tripping.

Ron(UK)

OK. Changed the capacitor but now I cant get the motor to run at all !!!!

Just to explain how its connected. From the switch/timer theres one wire straight to the motor, and two to the capacitor. Then two run from the capacitor to the motor.

The sole wire is live (I checked). What should be live into/out of the capacitor. Why two wires in and out?

Should the motor run with just the one live? What about earth/ground?

Can someone explain whats what?

(BTW. Think I knackered the timer now though - shorted it and blew the fuses etc.).

What you describe doesn't seem to have any neutral connection. Are you sure you haven't lost a wire somewhere? How many separate terminals are there on the old and new capacitors, not counting multiple connections to the same terminals?

Probably not without more info.

What further info do u need?

The single wire from the motor on the white plastic connector is the neutral, one of the wires to the capacitor should be live with the motor running, these change over when the timer reverses the motor. What model do you have, I will have a manual for it if you need it.

Peter

Hi!

Yes, quite a few of them do. I've seen a very few that didn't, but they would be an exception to the rule in my view.

William

Sorry did not read all Post Yes it was the capacitor. As you say give the motor a push and it runs This is what the capacitor does. Changed a few of these over the past year. BigGuyUK

WV447

So why 4 wires on the top of the capacitor? There are two on one side of the top with a plastic separator between these and two more.

Should both inputs be on one side and both outputs on the other?

There's probably two pares of terminals, with each pair connected together. This is so you can connect more than one wire to each of the two connections to the capacitor itself.

I had exactly this with a White Knight dryer. It was indeed the motor run (not motor start, apparently that's a different sort of motor) capacitor. I took it off (the big silver cylinder on top of the motor) and took it to a local motor rewinders where the bloke rummaged in a pile for a while and gave me a spare for a couple of quid.

That was ages ago and it's still running.